I just finished assembling my doors. My 74 has one 73-74 door and one 71 door. They both fit the car no problem. The newer door is noticeably heavier due to extra reinforcement of the horizontal crash beam, they added a second outside layer to the entire width of the beam. The door glass upstops are different, but also no problem if you stick with the upstop type that came with that year door. If the 70 outside weatherstrip clips on, then maybe my older door is a 71 because both my doors have the screw on weatherstrip. The forward vertical track for the door glass can be whatever year you have the parts for...I converted both my doors to the older "square block" style, only had to use matching track. All the other parts can swap to any year door. Hope this helps.
