The basic differences are 1970 had their own drainage hole system in door base with plug strips, and different end pressings where the labels are found, changed in 71.
All door skins are the same regardless of long or short handle used, possibly different thickness sheetmetal between early and late. 70-77 have the early power door lock solenoid position dimples, moved for the 78-81 actuator setup. Easy to reposition, don't just go drilling without checking.
The inside pressing of the doors changed in 75, mainly around the regulator and door handle. I believe this really only affects the type of inner door handle assembly and cup bezel used. Not sure how easily it can be modified or swapped etc, I guess plenty have had this issue over the years even if they didn't find out until assembly.
The inner crash bars were also increased in size over the years, possibly also around the 74-75 era. The area above door handle for lock switch was also depressed for clearance. This didn't move until 78, 77 was on dash, but door may have been that way in advance.
Here's some random pics from a PY post showing both doors. Black is 71, blue is 78. Still hard to compare at same time.
https://forums.maxperformanceinc.com...7&d=1200800125
https://forums.maxperformanceinc.com...0&d=1200800184
https://forums.maxperformanceinc.com...8&d=1200800125
https://forums.maxperformanceinc.com...9&d=1200800184
https://forums.maxperformanceinc.com...d.php?t=547747