[mcmlxix]

The 2wd and 4wd box is different... the pitman cannot be swapped. You can get any box from 69-87 c10 c20 c30 but there are still small differences in the power steering connections. SAE vs metric on the newer boxes...

For the trailing arm swap, I think you're just going to have to swap the crossmember over with measurements. I dont think there are any pre drilled holes....