[Zoomad75]

For what you are doing a 12bolt should work. Definitely go for stronger axle shafts for it as that would be your weak link, even more so with a tru-trac.

I've busted the original 12b in my old '75 K5 just driving down the street around the corner from my house though. Nothing screwy other than it was like 4 degrees outside and everything was super cold heading out for a snow run. I never took it apart but by the size of the exit wound on the cover it spit a tooth off the pinon or a spider gear. I wheeled it hard for a few years (open, with 35's) and never had a problem before. I can only chaulk it up to 40 year old original parts that had probably been stressed to the limit and the extreme cold finally fatiuged something to the point of failure.