After a quick, disheartening thought of gluing the seams on the seat pads, I ordered two vinyl pads and a vinyl seat back from Autos International. They came in very quickly and I started working on the repairs. I used copious amounts of contact cement that I originally bought to restore the dashboard, but the seat restoration needs a *lot* of contact cement, so be prepared! Don't use the spray stuff out of the can, use the stuff you get from a specialty fabric store that's specifically for gluing vinyl.
First I pulled the bad vinyl off both seat pads, and replaced it. Luckily I had a pneumatic stapler in my woodworking toolbox, because each pad takes about 50 staples to hold it in place. My friend Gary at G Rides took some time out of his work on Ferraris, Lamborghinis and Porsches to re-rivet the seat-holder-clips into place.
Then I went to work on the driver's seat. I stripped it apart and found some problems with the foam, so I repaired the issues before starting to put the new vinyl on.
The new seat cover was sized perfectly, and the result is great. Here are the completely new driver's seat, and the original passenger seat with new pad vinyl. The driver's seat is on the left, with a matte finish from the new factory vinyl, and the passenger seat on the right with a bit of shiny patina...
I also restored the seat slider mechanisms, cleaning them, grinding off rust and oxidation, repainting and clearcoating. Nobody will see these without sticking their head under the seats, but I know they're there and they look great!