76 duster clutch pedal will come up 2-3 inches off the ground but not all the way

Likely not part of the immediate problem but did you remove the over-center spring under the dash? Get a helper, push the pedal down, and stuff the spring coils full of washers or coins. Then just unbolt the one bracket and it will fall out.

Was it working "great' with the old clutch? If so, that would remove possibility that you have bent/ cracked/ damaged linkage. otherwise, yeh, too short a rod. "Back in the day" I put a Corvette diaphragm clutch in my 340 swapped 70 RR. It would not release. Turned out the clutch cover was just plain defective. So don't set aside that possibility