Upgrading your early Mustang with newer seats is a either a great mod, or necessity due to the lack of availability of original seat frames these days. Some of the more common choices are late model Mustang seats, or varied aftermarket seats.
I have/had the late 80’s Mustang seats in mine. When I pulled them out to replace the floor pans and install the roll bar, I about broke my back picking them up, they are heavy as heck, and they were not even electric. Trying to shave some pounds is always on my mind, not to mention cock-pit space with the roll bar install. Lets face it, the late model seats take up a lot of real estate compared to the originals, they are indeed nice seats and great for cruising but with the roll bar and need for speed, I needed to do something different.
Since my car will also see some street time with the wife, the standard plastic racers or metal Kirky’s were not going to do, also with the occasional ride in the back for the two young daughters, I wanted to keep a tilt/slide function so they could monkey their way through the roll bar – sounding like cake and eating it too?
My options, some pretty expensive aftermarkets or hit the salvage yards to see what I could find. Actually my friend who does a lot of road racing told me about Mazda Miata seats, so I took a look. Come to find out, they are plentiful, fit the bill for weight (about 15lbs each, lighter than the 5.0s), they are high back, low profile and sit low in the car, and yes the backs tilt. An added bonus, the factory slides are really nice, and quality stuff, and they have duel lockers to meet NHRA rules. Did I mention I can get them for 80 bucks a set!
Sounds good so far, here is where it gets interesting, how you get Mazda Miata seats to fit an early Mustang. They don’t bolt right in. The first issue, the Mazda seat pans are recessed into the car floor, meaning when you’re in the Miata, your butt sits in a well in the cars floor pan, about ¾ inch worth. The Mazda slides don’t have studs, they use bolts through tabs that are part of the slide frames. Finally, for some odd reason, the driver side is narrower than the passenger side – who knew. I didn’t until I got the passenger side to fit, only to find all my measurements were not going to work on the driver side.
Easy fix though with the problems of adapting these seats to the Mustang, first figuring out how to modify the Mazda slides to fit the Mustang floor pan bolt pattern while raising the pan up just high enough to clear the Mustang seat pan. (Even with this raising up, the seats sit lower or have a lower profile in the car than the 5.0 seats).
The passenger side was really easy, I found the factory Mazda locator pins fit perfectly in the Mustang bolt pattern, the center line of the slides on the Mazda passenger seat is only a 1/16 narrower than the factory Mustang slides/pattern. So I lopped off the end tabs, ground the locator pins off, then punched them back through the seat rails leaving some nice holes to work with, then using my old seat pan from my floor pan job, I measured and marked along the track where I needed the rear studs. I then drilled two more 5/16 holes in the rear of the tracks.
I took four 5/16 course thread Allen head bolts, dropped them into the tracks and installed 5/16 grip nuts on them. This solved two problems at once, creating four studs to bolt to the car, and the nuts raised the seat about a ½ inch off the floor seat platform, making the clearance issue go away. The tracks plus the nut were just right. I then went to the backside of the track and tacked the head of the Allen bolt to the track to keep it from pushing out or spinning, then I tacked the grip nut to the track to add some extra grip and duck taped a fender washer over the nut to keep the nut from working through the floor pan hole. It fell right into the bolt pattern. Passenger side done!
Not having taken the time to ensure the seats were the same bolt pattern (I assumed they would be), I quickly found out the driver side was not going to be so easy. I was 1 inch narrow overall on the seat tracks from the stock pattern. So I had to figure away to widen the track bolt pattern, and raise it up as well like the passenger side. The tracks were not wide enough to work with. Why not just re-drill the seat you say?
The seats had nice nuts welded into the bases, and there was not enough meat or metal surrounding these nuts to do this. I considered cutting the nuts out, and welding in new metal, with nuts, but I came up with a quicker/easier solution, since it was a two part problem, width and height.
I fabricated studs just like I did above on the centerline of the tracks, and put the 5/16 bolts through and installed the nuts, and welded the backside, these became my new locator pins. I got two pieces of 1/8” X 2”X 14” flat bar and scribed a line about ¾ of an inch along the inside edge, and located the distance of the locator pins, and drilled these two holes out to 5/16.
I then cut or ground away any high spots on the seat tracks, and laid the flat bars on the seat tracks flush. I then marked each side a ½ inch wider than the locator pins, and marked a new hold ½ inch back from the locator pin, essentially creating the Mustang bolt pattern ½ inch rearward of the locator pins.
I also drilled a few holes along the flat bar where there were little pins in the tracks; this would be a great weld area later.
I then put four 5/16 Allen head bolts into the Mustang bolt pattern I had just drilled, and put a nut on them to hold them. I had to weld a small tab on the back of the flat bar to fill a gap where the Mazda seats had a layer of metal drop off, so the flat bars would fit flush along the track. Once all of this lined up and looked good, I laid my old seat pan over it to check my new stud set up, it fit like a glove.
Having it all mocked up and fitting for trial, I still needed to get rid of the nuts on the locator pins, and the heads on the new seat studs so the flat bars would fit flush for welding. I tacked the locator pins into the seat tracks from behind like I did with the passenger seat. While I had the flat bar off, I tightened the nut on the new stud bolt really well, and then tacked the nut to the flat bar. I then cut the head of the Allen bolt off from the back of the flat bar, and ground it out a bit and plug welded the remaining stud to the flat bar. Then ground that flat.
I was now able to bolt the flat bar to the original locator studs, and draw if tight and flat to the tracks. I then welded the flat bar to the tracks along the front and rear, and through the plugs I had cut earlier. Once welded, I used my cutoff wheel to cut the locator pins off flush with the flat bar, and ground it out a bit, and plug welded those solid.
I checked it again with my old seat pan, worked great, dropped it in the car and it fit like a champ, put on my steering wheel and found that I now had plenty of room to clear the roll bar getting in and out with a 14 inch steering wheel.
The seats are really comfortable, they are narrow and don’t fill up the car, the shoulder harnesses wraps around the narrow back very nicely, and they look and work like they were made for the car. The seats are now at Tim’s Upholstery getting a nice new layer of light blue with medium blue inserts sewn on.
So if you’re thinking seats for your car, don’t discount the low profile foreign seats. I was sold on the Miata seats, but I also found Pontiac Fiero seats were available for the same price, and looked cool too, as well as some Nissan and and others.. If anyone one wants a set of nice 5.0 seats ready to bolt in, in dark blue and light blue inserts, shout out.
Work safe, and enjoy. Gydyup!
Gydyup - 67 Mustang Coupe
Today
