Its all available through Dynacorn . I ordered all the metal through Stang-aholics ,Ryan has all the part numbersWell, I found '67-'68 fastback rear seat frames, but not '65-'66. I also found R3 Performance Products, which bought out Thoroughbred International (or Thoroughbred GT) that made 'skeletons' for '65-'66 fastbacks.
R3PP was in California, but is now in Broken Arrow, OK which is close to me. Thoroughbred made jig welded coupe to fastback skeletons as well as coupe to fastback skeleton kits.
I called them at lunch and talked to someone who didn't say they wouldn't, but sure didn't sound like they were interested in selling me what I wanted for a self install.