I remember There was a thread a while back that showed a couple cars that did not have the pierce nut on the radiator support for the negative ground cable. Be curious to know for sure HOW they attached the cable to the support originally.

Actually there are several nuances to the 70 versus 71 and up cars.
door side impact beams in 71 and up - not in 70's
upper door frame window sweeps attaching differently.

hoods crumple zones as mentioned

hood hinge to hood bolts changed from a 5/16" bolt to a 3/8" bolt sometime late in the 70 to early 71 model year
parking brake cable routing is different 70 versus 71 and up is another clue