70-74
Have a "fuller" front grill and lower mounted turn signals
74.5-78
Have a grill with turn signal cut outs and the turn signals are mounted in the grill
I would say the gnose have a spot for lower mount turn signals. A conversion can be done, just have to remove the old turn signals and find some lower mount turn signals at a junk yard.
Oh yeah, As far as body size goes, 70-78 body kits are usually interchangeable.