If you really are interested, check them carefully for rust in the floors and front inner fenders. Tailgates (upper and lower) rust too, but can be found relatively easy.
Interior parts for the 2 doors are getting very thin on the ground, so any missing bits will likely be missing for a long time. They're even hard to find in the UK. Likewise, the doors are unobtanium. The good news is that they're aluminum and don't corrode much.
As to engine options, it's really down to your skills and what you want to spend. The Rover V8 is a good engine if properly maintained. You can swap in a GM v8 of almost any era, using a bell housing adapter from Marks in OZ. That will add about 150 lbs to the nose. The newer GM Vortec 4.3 V6 is also a reasonable option, it has similar power and weight to the Rover V8. The early RR's have minimal electronics, so engine swaps are easier than on later trucks.
If you have connections or deep pockets, you can source a diesel from the UK.
