I have a 65 C10 that I converted to disc brakes, 5 lug wheels, and installed a 3.08 rear end out of a 97 suburban. Couple of things to consider....
The disc brake conversion will most likely give you a wider stance by an inch or two as it pushes the wheels out. You'd have to find a rear end that would match this spacing unless you want the truck to look funny going down the road.
Also, consider a disc brake conversion may or may not match the wheel lug spacing. I bought my disc conversion and my rear axle before I realized the discs were 5x4-1/2 and the rear axle was 5x5.
You're trying to make changes you think will make your life easier but it could also be a huge pain in the rear in the long run
