Thanks for the definitive info. I have the truck now, and have decided that I like it and can make use of it if I can change a few things. I have a couple of questions, though:
The engine has been swapped out to a 350. I like the way it sounds and drives, but it still has the 4 speed transmission. It appears to be original, and works just fine. It is incredibly slow, though, due to the rear end gearing, I presume. As far as I can tell, aftermarket gear sets are unavailable for the 3/4 ton axle, so I'd like to get a rear end from a modern truck.
I understand that the overall width of the assembly will be larger, but I can be OK with that if it's only by a few inches because I am putting a flatbed on it. Does anyone have a suggestion for which truck I can get this from at the junkyard? I'd like to keep the 8 lug wheels, and i'm hoping that by swapping this out, I can drive it around town without starting off in 3rd gear. Thank you!