Right inner fender will also have weld-nuts for the horns on 70 & 71's, just holes or dimples on 72-74. Horns are off the latch tray support on the later cars.
I think the later ones also have more holes in general for mounting washer bottle, charcoal cannister, etc.
A/C & Non A/C are the same physically, there are just more holes used for A/C...water valve, air dryer, etc. Firewalls are different.
Steve