Are you building a rock crawler or a wet weather driver? Will you have big power and need the stoutest transfer case and axles or something mild?
I've seen a number of these trucks converted to four-wheel-drive.
There is one that you can walk under that has Rockwell axles under it. I've never seen it move and doubt very much its legal on the street. I've seen Grave Digger up close. This one is taller and has an original steel body instead of fiberglass over a tube chassis.
There is one I often see around locally, though it was on craigslist last year and may have moved out of my area. Its a long-box 1/2-ton GMC and based on crawling under it I'd say it has 70's 1/2-ton running gear on the stock frame. It was nicely done but never seemed to be a daily driver. It also changed hands quickly over the ten or twelve years I saw it around and I never managed to talk to an owner.
I've seen a number of them placed on S-10 4x4 frames with both V-8's and V-6's under the hood.
A project I've not talked about much here is putting a '54 GMC on an '87 S-10 4x4 frame. I have the frame in my shop, the cab, bed and fenders are on my trailer, and the engine, transmission and transfer case are in another truck parked next to my shop. I'm planning a look not unlike some of the tall 80's Toyota trucks I see around, but with a 454 under the hood to out power them pretty much all the time. Mostly the truck will be used as a bad weather driver and for moving my trailer around (usually empty) where my bigger truck gets too crowded.
The right choice for you is the intersection between what is practical from a build standpoint combined with what you really want the truck to do.
