71 and 72 hood question

On E-bodies the crumple zone change happened mid-'71. The '70 hoods did not have a crumple zone, the early '71 hoods were the same as '70 hoods. Then mid-'71 a crumple zone was added and continued going forward. The bolt size changed as well, the '70 used smaller bolts than the mid-'71 and up.

As for the A-bodies, well, the hoods I have are all '70 or ''71 and they've all been the same. 73+ was different, but that went along with the complete redesign of the '73+ hoods. I suppose the trick would be to compare a '73+ Dart hood to a '69 Barracuda hood, but I think the hinge changes are the biggest difference.