ID rear end in my 1967 C10

[Peanut74]

Thanks for the pictures GASoline71 they are a big help. I did jack the rear end up and spun the wheel. One went clockwise and the other counter clockwise so that confirms its nonposi. Also, tried to confirm the gear ratio but that didn't go well. Kept getting conflicting results. But based on the cracking of the rubber bushings its the original hard pan.

So I've come to the conclusion that its the original rear end. I would open it up but will do that after it gets back from the frame shop. Started the trucks disassembly and noticed that the frame rails were not vertical and looked a little bit off. So I want to have that checked before I start making mods to it.