Out of curiousity, what color was the car ? Any remnants of the top cowl painting ? Depending on the stripe color, might be another clue if you can find the beginning paint layer.
I looked at a shell years ago that the then-owner didn't have clue as to what the car was built as (missing drivetrain except for the 12 bolt and four leafs), disc brakes, dual exhaust plate, single 3/8" fuel line, correct Pitman and Muncie cable routing, and an all-white cowl top. Car got away before I could buy it, obviously an early non-X code (late November) Z if I've ever seen one. Hate the ones that get away (when the stars just don't line up !).
Regards,
Steve