I'm not sure of the years. They would have been 1/2 tons. Been told 3 speed trans only. If your lucky they will be 3.78... most were 4.11 or deeper. Now if your going to run an overdrive trans, deep gears is what you want.
The one I have is 3.78 and was out of the donor truck. ( It was laying under a van with part of it sticking out when I spotted it. )The junk yard I got from had no info on it. Got it home and took it apart, it's rusted up. I think it can be saved.