[Lees68GMC]

Probably not a lot of help at this point, but here's my experience.

Mine is a 1968 GMC SWB with Leaf Springs and a 10 bolt corporate rear-end. 6-lug wheels. After I made the decision to lower front with drop spindles, I found a 1974 1/2 ton Chevy in the Wrecking yard and got Rotors, Calipers upfront and the complete 12 bolt rear-end, drum to drum for a total of $150.00. I could see just trying to freshen up the old 10 bolt and really limited parts availability Today and into the future, this would be a cheaper way to go.

The 1974 12 Bolt was 2" wider with identical, bolt up spring perch locations. The wider rear worked better because with stock off set 15 X 8 wheels and 275-60-15 BFGs moved the tire sidewalls away from inner fender wells, outboard where there is plenty of room. Shock mounts had to be cut off the 74 as that was the first year for the asymmetric rear shock mounts. Also gave me 5 on 5 lugs to match the 5 on 5s up front, sold my 6-lug wheels.

Parts every where, reasonable for GM 12 bolt rears.