[1985 CCX]

These leather seats, as Nick said, are 25yr old CCX so you need to find a toasted CCX or have a set made. I know ERA makes the frames and has extensive measurements. Remember 427 cars used Naugahyde and 289's leather.

I would say source from: (My advice = a great seat makes a huge difference. Don't skimp here)
ERA
KMS

Would be my top choices.