The '72s (I've seen some 71s with them as well)have an additional screw just below the window on the inside to help hold the vent window and keep it from rattling and keep the door from cracking around the vent window. The 72s also had different door panels that used plastic clips and used different holes as a result.
It was common practice for people to add a screw in that some location on the earlier doors but most of those had a plastic piece that matched the profile of the door. So your current doors may have something similar.
All the doors will interchange, the door panel holes can be tricky when trying to put 71 older panels on 72 doors, I've always just used 72 door panels. 72 door panels on pre 71 doors requires the correct holes to be drilled and is pretty simple.