Others have more knowledge on this, but some tell-tales of an original fuelie car are (1) the original radiator support (hole and screw holes showing threads for the "S"-tube) although such could have been added, (2) the left inner fender would have holes and tapping plate for the air cleaner, (3) the front fenders would show holes for the F.I. emblems (or perhaps they were glassed over, but visible from inside), (4) a pig tail with a connector coming out the main engine harness around where the throttle linkage is - supplied voltage to the fuel bypass solenoid.
good luck
