Seat rebuild question

The medallions are originals. I managed to break one of the three I have tried to take apart. I still have at least one more, possibly three more. The convertible only needs three so I'm good.

Covers are Legendary, but are now OLD. Bought nearly 20 years ago so I'm not sure that they'll fit as vinyl does shrink. They are still very pliable, though. Quality looks good. New foam looks good. Next up is my Barracuda and then the GTS. Hopefully, I'll be good at it by the third car. Gonna attempt the top on all three, as well.

Years ago, I worked for a company who upholstered vinyl pontoon seats. We would place the seat covers in an enclosed cabinet with red heat lamps for a few minutes prior to installation. laying these in the sun or warming them up with a hair dryer would help them stretch a bit easier when you go to install.