Tried to post this last night, but my account is all screwed up right now. So I registered again.......
It was 77, 77-91 doors are the same. You will need to change the complete door. 73-76 doors can't be used for the power motors. Here is a pic of the comparison. I can tell you what the problems will be if you can tell from the photos.
73-76 door
77-91 door
There are also 2 versions of the power motors. The early style 77-80 are a little stronger/bigger motor than the latter.
------------------
Chris Lucas
www.captkaoscustoms.com