Add PDB and C-stripe to the list, also optional 390 4v. The 289 4v (A or K),was the '65-'67 base GT engine.
Don't quote me on this but, I think 3 spd manual throws the GT thing out the window. If the car is Metuchen born, look for the buck tag on the inside passenger apron. It will have the letters GT on it.
GT's in 68 were only available with a 4 barrel V8 engine, (in 67 they could be had with any V8-also in 68 the California special GT coupes could be had with any engine-6cyl on up). Many GT's had originally 3 speed trannies, the 4 speed and automatics were optional.Here is what the Mustang Recognition guide shows included in 68 GT's:
*GT ornamentation - front fenders
*GT pop open gas cap with red letters
*Low restriction dual exhaust with chrome quad outlets
*4 inch fog lights in grille
*GT "C" stripes along body lines -new for 68
*GT chrome styled steel wheels with red GT letters in center cap
*F70X14 wide oval white sidewall tires
*Heavy duty suspension
*chrome engine components-390/428 engines only
Notice disc brakes were not included for 68, they were now optional, many 68's are confused with being GT's because they have the foglights in grille as part of the Sprint package offered in Ford's "See-the light sale" in the spring and summer of 68.The sprint package included the GT side stripe, pop open (non-GT)gas cap, wide oval tires on styled steel wheels-plain centers and the grille mounted fog light like the GT's. 6 cyl Sprint cars did not recieve the fog lights or special rims and tires.If the car was made in the spring/summer of 68 it could have possibly of been one of these, Ford was trying to recover sales after the big strike.