Replacement Seat Foam

I just reupholstered the sport seats in my '89 GT a few weeks ago - same seats you have.
I stripped mine down to the bare metal, powder blasted the frames, repainted and rebuilt with new foam & fabric. They came out great and look original - almost as ugly as they did from the factory (hideous red interior).

The seat bottoms aren't too terrible to do. Backs were a little more difficult to make look good.
You'll need to be really careful removing the old upholstery to be sure you don't damage it. My fabric & vinyl was so old it didn't have much stretch to it so I had to cut some to remove it (I didn't put in much effort as I didn't plan on re-using it). If you hit it with a heat gun or hair dryer I think the vinyl would stretch enough to come off without tearing it up.
While you're pulling it apart just keep track of where the metal rods are inside the seat and where the hog rings are located.

Replace the foam & reverse the process.

The replacement foam isn't an exact match for the factory foam so you'll need to prepared to pad out the parts that don't fit exactly with some polyester batting.

I have a ton of pictures of my teardown around here somewhere. If you think it would be helpful to see what's inside the seat let me know and I'll post 'em.

Here's a shot of the foam after it was out of the car just so you know what I'm showing you in the pics;



Arrow A - There's a metal rod with 2 "humps" formed into the seat foam, one on each end that the metal rod (B) slide under.

Arrow B - fairly heavy metal rod that fits in a pocket sewn into the upholstery and forms the deep seam along side the side bolster. It's trapped by the rod (A) in the back and clamped to the seat frame in the front.

Arrow C - another metal rod that forms the horizontal seam in the seat. It's connected to a plastic rod formed into the seat foam using 3 hog rings.

The red lines show where the metal rods will be.




Start by removing the plastic clips from the seat base.



Remove the roll pins from the knee bolster bracket and get that out of there. I trashed mine getting them out and ended up replacing them with 1/4-20 bolts. Worked fine.



Carefully pull the upholstery up over the side bolster. You're going to need to heat the vinyl to get it to stretch.
In this picture you can see where the front of the seat fabric is held to the frame by 3 hog rings.
You can also see the 2 rods that make up the side bolster seam & the clamps that attach them to the frame.
Try and save these clamps when you remove them - It'll make putting things back together much easier.



Better shot of the clips.



The side rods (part B in the first pic) partially removed from their pockets in the upholstery.



Remove the 3 hog rings from this final rod (part C in the first pic) and the seat cover is off.



FYI, This is what the small rods look like in the pockets.


I hope this helps - Let me know if you have any other questions.