Just about anything will fit with the right brackets.
I had a set of Flofits in my first '66 vert. This time around, I decided to save and picked up a set of 87 Supra seats (actually made money on that deal but that's a different story). I'll have to fab some brackets but they will fit.
Pro Car by Scat and Corbeau have brackets for classic stangs. Actually, only one of those brands might, I can't remember, but check them out, they both have decent websites.