by Richard Cordon III

Introduction
What do floor jacks, jack stands, and rust all have in common? They're all arch enemies of the 1965-1970 Mustang floor support. Perhaps your Mustang has fallen victim to one or more of these rivals. Whatever the case, early Mustang factory floor supports are a commonly replaced item at RatStang Restorations. Damage to the front floor support is primarily due to Ford's use of thin 18 gauge steel during the manufacture of the early pony car. Unfortunately, 18 gauge steel is too weak to routinely support and lift a 2500 pound vehicle without causing damage.

	1965-1970 Ford Mustang 14 Gauge Replacement Floor Supports Originally equipped with thin 18 gauge frame supports, early Mustangs can benfefit greatly from stiffer 14 gauge supports like these "M121" units.

In order to cure the problems associated with age and the inherent weakeness of stock Mustang floor supports, this article will show you how to install 14 gauge steel replacement floor supports to decrease the chance of damage when putting one of these cars on a jack or jack stands. The procedure also offers the opportunity to stop rust that builds up between the frame supports and the front frame extension.

Using 14 gauge floor supports (aka M121 floor supports) also helps stiffen a Mustang's unibody frame construction. M121 frame supports are sold by many Mustang parts distributors and are one of the lowest gauge steel units in production. For those thinking of adding subframe connectors to their Mustang, upgrading to stronger floor supports makes perfect sense. Subframe connectors can only be as stiff as the parts they are connected to, which makes the stock 18 gauge supports undesireable in this scenario.

Removing and installing floor supports around existing floor pans is a more delicate process than doing the install during floor pan replacement. This is due to the fact that you have to be careful not to damage the floor pan during the process. All of the work performed for this article was done on a 1966 Mustang. This particular Mustang had previously replaced floor pans, so the replacement was done around installed floor pans. In addition to basic safety gear (eye, ear, respiratory, and skin protection) this entire project was done with the tools found in the following table.

Removal
Unlike most do-it-yourself automotive adventures, when doing bodywork the "teardown" or removal phase is not one to be taken lightly. In other words, removing Mustang floor supports takes more brains than "Cletus" and a Sawz-All can muster up. You've got to be wary of protecting floor pan sheetmetal when removing these pieces. The adjacent photo shows the tools used specifically for the removal process. Pictured are the Long Stroke Air Hammer, Air Hammer Chisel Set, Brass Hammer, Large Flat Blade Pry Bar, and Vice Grips. Here's how we did it.

This shot shows the passenger side floor support after being cleaned with wire brush. The chassis is fixed in a frame rotissere.		This shot shows the driver's side floor support. For demosntration purposes, we will be showing you how we did the work on this support.
Here we marked a cutline a half-inch from the rear edge of the front frame rail (upper right). The cut would be made with a high speed cut-off tool and an air hammer with a cutting chisel.		The cut was made all the way around the floor support. A second cut was made about an inch from the transmission crossmember. Both cuts extended all the way around the floor support up to about a quarter of an inch from the floor pan.
A third horizontal cut was made a quarter inch from the floor pan extending to the first and second cuts on both sides. Due to bad angles, most of these cuts were made with the air hammer and cutting chisel.		Next, a horizontal cut was made from the point of the removed piece to about an inch from the opposite side of the transmission crossmember.
The next cut was a vertical cut over the bottom edge of the floor support along-side the transmission crossmember. Then a horizontal cut was made running along the floor support about a quarter inch from the floor pan.		The cut continued around the floor support until the cut met the first removed piece. This was done maintaining the same quarter of an inch gap from the floor pan.
Here's the removed piece. The floor support's entire spot welded lip remained attached to the floor pan. The delicate Prying and Rocking Technique (see following section) was used to slowly stress and break the welds to remove the spot welded lips.		With a large pry bar and a brass hammer, we stuck the pry bar behind the remaining lip and hit the pry bar inbetween spot welds. With a slight rocking motion, we stressed the steel around the welds and broke it, grabbing the lip with vice grips and rocking it as we did the prying.