Welcome from KC
Check other salvage gm vehicles for the rear door actuator. I found a actuator for my 86 gmc out of a corvette close in year exactly the same. Mounting bracket was different but I had the one from my truck.
Right front, dark green+, light green-
Left front, gray+ tan-
Right rear, dark blue+, light blue-
Left rear, brown+, yellow-
This is the speaker wire colors for my 86.