That Was Then, This Is Now: The Shelby Mustang

Race car driver. Mechanic. Tuner. Designer. Manufacturer.

There is seemingly little in the realm of the automotive industry that Carroll Shelby didn’t accomplish. From winning the 24 Hours of LeMans as both a driver and a constructor, to founding his eponymous automobile company, Shelby somehow always managed to succeed where others had failed.

In today’s world where terms like “icon” and “genius” are bandied about far too liberally, these adjectives actually fail to convey the astonishing vision and sheer audacity of the down-home, former chicken farmer from rural Leesburg, Texas.

When contemplating the man’s legacy, it is challenging to pick out a lone example amongst his creations as being his magnum opus, what with the Shelby Cobra, Shelby Daytona, Ford GT40, Dodge Viper, and other high-performance cars on his resume. But when you consider which is the most lasting, celebrated, and enduring of his four-wheeled progenies, it is difficult to point to anything other than the Shelby Mustang.

Carroll Shelby pictured behind the wheel of the first Cobra built, CSX2000. (Photo courtesy of Shelby American.)

Born in 1965 out of a concern that Shelby’s friend and father of the Mustang, Lee Iacocca, had that the Mustang was not sufficiently sporting enough, Shelby’s modifications to the Mustang transformed it into a legitimately snarling, road and track beast.

Unbeknownst to either man, they had, in the process, created an automotive exemplar that would see several future iterations spread across nearly sixty years, and stand throughout as the very personification of American muscle.

As we have done in past editions of That Was Then, This is Now, this month we’re going to examine the history of Shelby’s most famous steed, and compare the models of the past to those of today. So belt in, because this promises to be a thrilling ride.

(Photo courtesy of Mecum Auctions/CarBuzz.)

Carroll Shelby already had, by the time of the Mustang’s launch in April of 1964, an association with Ford via his use of the company’s engines in his Cobra roadsters, and through having helped to develop the GT40 race car that would go on to beat Ferrari at Le Mans in 1966. As such, he and his company, Shelby American, were the obvious choice for Iacocca to turn to transform the Mustang into a true sports car.

A deal was struck, and in August of 1964, the first 110 Mustang Fastbacks arrived at the Shelby American garage in Venice, California.

1965 Mustang Fastbacks being converted into GT350s at the Shelby American shop in Venice, California. (Photo courtesy of Shelby American.)

The first Shelby Mustang, given the random moniker “GT350” for the number of feet between the race and production shops at Shelby American, was blessed with a 289 cubic-inch K-Code V8 engine which bumped the Mustang’s horsepower to 306 ponies by virtue of a Holley four-barrel 750cfm carburetor, a Hi-Rise manifold, cast-aluminum valve covers, and oil sump, a larger radiator and tubular Tri-Y exhaust headers feeding short side pipes.

A four-speed, Borg-Warner T10 transmission with close ratios and a ratchet-type limited-slip differential were standard equipment.

The ’65 GT350’s K-Code 289. (Photo courtesy of MustangForums.)

Other upgrades included a quick-ratio steering rack, oil coolers for the differential, semi-elliptical leaf springs, a beefier rear axle, more robust anti-roll bars, Koni adjustable shocks, and Kelsey-Hayes front disc brakes.

The cars featured a number of exterior modifications as well, consisting of a fiberglass hood with functional scoop, and 15-inch Kelsey-Hayes mag wheels shod with Goodyear Blue Dot tires.

The 1965 Shelby GT350. (Photo courtesy of Mecum Auctions.)

The GT350 was only offered in Wimbledon White with Guardsman Blue rocker panel stripes. Roughly thirty percent of the cars that left the Shelby garage came with the matching Le Mans-style racing stripes across the top.

For those who craved an even higher echelon of performance, 34 GT350R models were made packing 360 horsepower.

Carroll Shelby and his handiwork: a 1966 GT350 and a Shelby Cobra. (Photo courtesy of Shelby American.)

1966 was largely a continuation year for the GT350, with changes being limited to new colors, functional brake scoops on the flanks, and new rear-quarter windows. A few consumer-friendly options such as an optional SelectShift 3-speed slushbox and fold-down rear seats were offered.

The GT350H produced for Hertz Retal Cars. (Photo courtesy of BringATrailer.)

Additionally, the famous Shelby GT350H models were built especially for Hertz Rental Cars that year, featuring a black and gold color scheme. Wanna-be racers could then trash someone else’s Shelby for a weekend at their favorite track.

1967, however, was hardly a carryover year. Ford had completely restyled the Mustang, making it both larger and heavier. Shelby took this as an opportunity to do what he originally wanted with the ’65-’66 cars, and make the Shelby’s aesthetics distinct from their lesser Mustang brethren.

The 1967 Shelby GT350. (Photo courtesy of Barrett-Jackson.)

He outfitted the ’67 GT350 cars with fiberglass body pieces, including an elongated nose, a hood with twin functional scoops, and four body side intakes located at the quarter windows and ahead of the rear wheels. A fiberglass tail featured an integrated spoiler and sequential turn-signal/tail lamps pilfered from the Mercury Cougar. Twin, high-beam headlights were mounted in the grille.

More than just giving the Shelby Mustangs a unique appearance, the changes to the front end of the car allowed for a big-block engine to be fitted. This marked the genesis of a second Shelby Mustang model, the GT500.

A stunning 1967 Shelby GT500. (Photo courtesy of BJ Motors.)

Shoehorned into the GT500’s engine bay was an FE-series 428 cubic-inch Police Interceptor V8. Shelby outfitted the motor with twin 600-cfm Holley four-barrel carbs atop a cast-aluminum medium-rise intake manifold raided from Ford’s 427. Output was an underrated 355 brake horsepower and 420 lb-ft of twist.

Mated to this lump was a choice of a RUGS-1 four-speed manual transmission with a limited-slip differential, or a three-speed auto.

The big 428 Police Interceptor V8. (Photo courtesy of Barrett-Jackson.)

Stiffer springs front and rear, a larger anti-roll bar, Gabriel adjustable shocks, and front disc brakes with drums in the rear were all standard equipment. A choice of three different 15” wheels was offered, all fitted with Goodyear E70-15s.

Inside, the GT500 received an upgraded dash, with an ammeter and oil pressure gauge located in the center. A backseat and full roll cage – the first ever fitted in an American production car – were standard.

Inside the GT500. (Photo courtesy of Barrett-Jackson.)

Externally the GT350 and GT500 looked identical, save for the call-outs on the rocker stripes.

1968 saw minor exterior changes, with the primary difference being a new hood with revised scoops at the leading edge. Under this, though, the 1968 GT350 had its 289 replaced by a 302ci V8, and beginning in April of 1968, the GT500 received a new 428 cubic-inch powerplant known as the Cobra Jet. Cars equipped with this motor were known as the GT500KR for “King of the Road.” 1968 also saw the introduction of convertible versions of the GT350 and 500.

1969 would again bring major aesthetic changes to the Shelby Mustangs.

The 1969 Shelby GT350. Photo courtesy of Coyote Classics.)

Whereas the first-generation GT350s were dyed-in-the-wool race cars, and the second-gen cars somewhat more road-friendly, a decision was made to make the third iteration a grand tourer. This resulted from the fact that Ford had largely taken over Shelby design decisions, and decided that Shelbys needn’t be track-oriented anymore, since the Boss 302 had become Ford’s primary race Mustang.

The ’69 Shelbys again received body modifications to differentiate them from standard Mustangs. With its front section elongated by four inches, a full-width, recessed grille encompassing the dual headlights, and a rear dominated by Thunderbird taillights and center-mounted twin exhausts poking out through the bumper, only the roof, doors, and quarter panels remained from the standard Mustang.

A love-it-or-hate-it look. (Photo courtesy of the American Muscle Car Museum.)

It was a love-it-or-hate-it look, and many gravitated towards the latter sentiment.

Mechanically, the GT350 received the M-code 351 Windsor V8 good for 290 ponies and 385 lb-ft of torque, while the GT500 once again received the fire-breathing 428 Cobra Jet.

The 351 Windsor V8. (Photo courtesy of Fast Lane Classic Cars.)

Behind the motor, one could find either a close-ratio, four-speed Toploader manual, or Ford’s C6 three-speed slushbox.

Gone were the race-bred suspensions of the Shelbys of the past, and in their place was a more supple setup, consisting of independent upper A-arms with stabilized lower control arms, coil springs, adjustable shocks, and an anti-sway bar in front, and a Hotchkiss-type live axle with leaf springs and adjustable shocks out back.

An ultra-rare ’69 GT500 convertible. (Photo courtesy of Mecum Auctions.)

A convertible option continued to be offered.

By 1969, Carroll Shelby had tired of the Mustang program and convinced Ford into discontinuing it after that model year’s production run was finished. Unsold ‘69s were given new VINs and marketed as 1970 cars, but no new Shelby Mustangs would be produced, marking the end of a legendary chapter in the performance car story.

But as with many things in life, the end is never truly the end.

The 2005 retro-themed Mustang GT concept. (Photo courtesy of Mustang Specs.)

With the retro-styling craze firmly gripping the automotive industry in the early 2000s, Ford saw fit to release their own throwback model in the form of the fifth generation Mustang in 2004 as a 2005 model. The car was greeted with universal acclaim for its modern interpretation of the ’67-’68 Mustang body style.

What better time and car could there be to inspire Ford to resurrect a legendary model from its history?

So it was that at the 2005 New York International Auto Show, Ford unveiled the new Shelby Cobra GT500. Designed by Ford’s Special Vehicle Team with Carroll Shelby on board as Senior Advisor, the new GT500 was the most powerful factory-built Mustang to date.

The production 2007 GT500. (Photo courtesy of NetCarShow.)

The production version hit the streets of America the following year as a 2007 model in both coupe and convertible versions. Replacing the Mustang GT’s 300 horsepower 4.6 liter SOHC three-valve V8 was a supercharged 5.4 liter, 32-valve, twin-cam V8 that pushed out 500 horsepower and 480 lb-ft of torque.

The engine featured a Roots-type supercharger adding 8.5 pounds of boost, a water-to-air intercooler, a forged-steel crankshaft and connecting rods, aluminum pistons, aluminum cylinder heads, and a low-profile intake manifold.

The 2007 GT500’s supercharged 5.4 liter V8. (Photo courtesy of Stephen Foskett.)

Backing the engine was a heavy-duty Tremec TR6060 6-speed manual gearbox, and at the rear, a modified 8.8-inch diff containing a 3.31:1 ratio with limited slip.

Stiffer springs along with Tokico struts and shocks were installed that sharpened the handling, as did stiffer stabilizer bars front and rear.

On the exterior, a new front fascia resided with a large grille, round fog lamps below the turn signals, and an air splitter at its base. A powerdome hood with heat extractors replaced the standard GT part. At the rear, a ducktail spoiler and a diffuser beneath the bumper were present to add downforce at speed.

The 2007 GT500’s interior. (Photo courtesy of Motor1.)

All in all, the new GT500 lived up to its forebears, providing excellent performance and standout appearance, largely owing to technologies and materials that were non-existent decades before when the Shelby Mustang was first unleashed.

But Ford wasn’t done with tipping its hat to the past, as a Shelby GT-H model was released in a black and gold color scheme, as a tribute to the original ’66 GT350H.

In 2010, the GT500 got a boost to 540 horsepower and 510 lb-ft of torque by virtue of a cold air induction system, and a year later received another ten-horse boost courtesy of revised tuning.

The raucous 2013 GT500. (Photo courtesy of Jalopnik.)

With the horsepower wars heating up in 2013, notably led by the Chevy Camaro ZL-1 and its 580 ponies, SVT engineers bored out the GT500’s now all-aluminum engine to 5.8 liters and swapped in an Eaton TVS supercharger, which combined to produce a raucous 662 horsepower and 631 lb/ft of torque. For the first time, a factory Shelby GT500 was a genuine 200mph car.

Sadly, this would be the last Shelby Mustang that Carrol Shelby had any input on. The great man passed in 2012 at the age of 89, after suffering from a heart ailment for decades.

In 2015 Ford went away from retro styling with the release of the all-new, sixth-generation S550 model. Although the contemporary styling was certainly news, for gearheads, the fact that the Mustang was finally given independent rear suspension was the resounding change. Ford wasted little time in taking advantage of this for their forthcoming Shelby versions.

The restyled 2016 GT350. (Photo courtesy of BringATrailer.)

The 2016 Shelby GT350 and GT350R can be viewed as Ford finally going back to the Shelby’s roots, heavily redesigning the Mustang to produce a true road and track terror, as opposed to just a souped-up version of the standard GT.

Starting with the mechanicals, the GT350 was bestowed with a naturally aspirated, racing-style 5.2 liter, flat-plane crank, 32-valve V8 that revved to an astounding 8200 rpm on its way to producing 526 horsepower and 429 lb-ft of torque.

Great attention was paid to making the engine extremely drivable for both street and track use with an exceptionally broad torque curve. Further underlining Ford’s serious intentions was the fact that the car was only available with a TREMEC 3160s 6 speed manual transmission. A robust, 3.73:1 ratio, Torson helical differential transmitted power to the ground.

The business end of the 2016 GT350. (Photo courtesy of CarBuzz.)

The GT350’s front track was widened, and spring rates and bushings recalibrated, along with a reduced ride height. Continuously controlled, hydraulic, MagneRide dampers were standard.

15.5-inch, two-piece front rotors with 6-piston Brembo calipers lived up front, while 15-inch ones with four-piston calipers lived out back for serious stopping power.

Typical Shelby modifications, such as a unique front fascia, additional venting, and driver-focused interior extras were all present.

The 2016 GT350 was a highly capable track car, but for those who craved even more, an “R” package was made available which harkened back to the ’65 R model.

The GT350R was a track focused car. (Photo courtesy of Mustang Fan Club.)

The GT350R was truly a race-focused car, and as such, its add-ons consisted of featherweight carbon fiber wheels shod in Michelin Pilot Sport Cup 2 rubber, a more aggressive front splitter, rear wing, and side skirts, and an air-to-oil engine oil cooler.

Weight loss was also a priority in the GT350R, and 130 pounds were shed by removing the air conditioning, rear seats, stereo system, trunk floorboard and carpet, exhaust resonators, backup camera, and emergency tire kit.

All of these modifications made the GT350R the quickest, and most nimble Shelby Mustang in history, if not the fastest. That title would belong to the latest and most powerful factory model to date – the 2020 Shelby GT500.

The 2020 Shelby GT500. (Photo courtesy of CarBuzz.)

Launched a mere month before the world found itself gripped in a pandemic, the GT500 was a brutish beast.

With an ultra-aggressive, nearly angry-looking front fascia, flared fenders, a massive hood-mounted heat extractor, and a rear spoiler for the ages, the GT500’s appearance needed a heck of a powertrain to justify its looks. Ford did not fail to deliver in that department.

The “Predator.” (Photo courtesy of

Under the hood lurked a hand-assembled 5.2 liter, cross-plane crank, “Predator” V8 topped with an inverted 2.65-liter Roots-type screw and air-to-liquid intercooler that produced 760 horsepower, and a stump-pulling 625 lb-ft of torque, making for the most powerful Ford vehicle ever.

Transmitting all that power was a TREMEC-sourced 7-speed dual-clutch unit with paddle shifters, a carbon fiber driveshaft, and a stout rear end with 3.73:1 gears.

The view most competitors would have of the 2020 model. (Photo courtesy of CarBuzz.)

For slowing down this rampaging bull, Ford fitted 6-piston Brembo calipers and massive, two-piece 16.5-inch smooth ventilated brake rotors at the fore, and 4-piston Brembos with two-piece 14.5-inch rotors of the same ilk aft. 20-inch Michelin Pilot Sport 4S tires were mounted on 20″ black aluminum wheels.

Revised suspension geometry and next-generation active MagneRide suspension was standard, offering the GT500 the highest-ever lateral acceleration from a Mustang.

The 2020 GT500 with the Carbon Fiber Track Package. (Photo courtesy of Edmunds.)

Two handling packages were available, including an $18,000 Carbon Fiber Track Package that came with 20×11.5-inch carbon fiber wheels, custom Michelin Pilot Sport Cup 2 tires, a massive, adjustable exposed carbon fiber track wing, splitter wickers, and a rear seat delete.

Performance of the 2020 Shelby GT500 was merciless, with zero-to-sixty falling in 3.2 seconds and the quarter-mile blurring past in 10.7 seconds.

Will this be the last Shelby Mustang? We’ll have to wait and see… (Photo courtesy of Hemmings.)

With more stringent CAFE standards on the near horizon, this GT500 might prove to be the most powerful, and perhaps the last internal combustion Shelby model made. The announcement of the 2024 Mustang in the fall of 2022 made no mention of Shelby versions, and instead promoted a 500 horsepower Dark Horse model to top the lineup.

While the 1967 GT500 is one of my dream cars, it goes without saying that many of the Shelbys produced post-millennia are better cars with far more prodigious power and better handling.

This is clearly an instance where now beats then, hands down.

About the author

Rob Finkelman

Rob combined his two great passions of writing and cars; and began authoring columns for several Formula 1 racing websites and Street Muscle Magazine. He is an avid automotive enthusiast with a burgeoning collection of classic and muscle cars.
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