I have a set of Iggee seat covers on my 3000gt. Good fit and look nice. I got the black leather ones and the set for the fronts was around $200. They make them for Mustangs too but not sure on the fit.
I wouldn't want to get in trouble for linking, so all I can say is google it. They make reproduction upholstery for Mustang, Camaro, and....VW. Good guys, I talk to their reps at a lot of the car shows I work.
Yeah no biggie. Check them out if you're in the market. The seats in our cars were foam injected, instead of fitted upholstery over foam, and TMI has perfected "re-popping", or reproducing those seats. Kind of considering the Mach 1 seats myself..