This is a fairly easy swap. I have a 1973 W-100. It is a complete bastard!!! The only original parts are the frame and X-fer case.
I pulled the windows, regulators w/motors, wiring harness, and switches of an 85 R/C from the J/Y. I also cut the inner door skin off one of the donner truck doors to use as a template for drilling the new holes to mount the new regulators/motors. Drill new holes, and mount the regulators/motors. The difference in the windows are the track at the bottom. The power windows have longer tracks. The wireing harness was basically a separate system from the main harness on this truck. I pulled the entire harness, disconnected the power from the fuse box, and the ground from the grounding panel behind the dash to the right of the steering column. Intsall the harness and supply power and ground. The harness has the relays and all. The system works great. I've had them in for over 3 years, without problems. The hardest part was finding the switches. I got mine from a 79 or so Cordoba. Any large 70's early 80's Chrysler Corp 2dr will do. I didn't know of RCC when I did this or I would have done a How to.
When I purchased the "Beast", it was a stock truck with a 318/NP435/devorced NP205. There was no factory options. I got it form the original owner with only 70k miles. I have since installed P/S, A/T, P/B, Fac A/C, C/C, P/W, P/L, Sun roof, 79 quad rad support/grill, D44HD front, D60 rear, 79 Step Side bed, 100amp Alt, 4" 3/4 ton lift, 3" body, 36x12x16.5 Hummer tires, and so many other things I can't remember. If anybody has any questions let me know.
Manny