Please don't take this as a knock on your car, but I honestly don't think a C-code fastback is worth an original restoration. How do I know? I have a '68 C-code fasback! Mine was a 91,000 mile original I purchased from the original owner, a 93 year old woman. It was garaged every day of it's life until she moved into a rest home two years before I got it. It would have been the perfect car to restore, rust-free, all the original stuff, date-coded everything, all the service reciepts, etc. If the car had been a big block, four speed GT or something things might have been diffferent, but it was a bare-bones Mustang with nearly nothing to make it special except the fact that it was a fastback. Would it have been worth more if it were restored to stock? Not likely. Build what you like, it'll still be a nice car and you won't have any trouble selling it later if you make some well-thought out choices like discs and R&P steering.