My 65 GT Fastback is all original and the engine has never been opened (the car has 110,763 miles at last fillup). I have the original window sticker, invoice and owners manual.
My 66 GT Fastback with the Pony interior 'K' car is all original and the engine was rebuilt about 1992 (this one has 79,011 miles at last filup). I have the original owners manual and the first Cal registration showing an October, 65 date registration date.
Is a big deal? You bet! Does it add value? It do.
My 'driver' is a 66 hardtop (196,017 at last fillup). Nothing special except I added a 4 channel stereo.