I used a Dana 44 limited slip with 3.55 gears and 6 lug drums from a '67 GMC in my '59. It worked really well in mud and snow when in the GMC with a 305 v-6, but I'm not sure it would be stout enough if you're building it up for drag racing. Pretty easy swap. I had to weld up spring perches, re-locate bracket for the brake line tee to the left side, and adapt the ends of the park brake cables to work with the backing plates. Used the original '59 lower shock mounts that fasten on the bottom of the u-bolts. Haven't drove it yet though as the rest of of the truck is still under construction.

Joe McNeel

http://mcneelnet.com/~jmcneel/59.html