I am happy with my 48 3600. It sounds like I have bigger calipers and rotors though. I did a back axle swap, used a 2004 chevy 2500 axle with disc brakes. In the front I have the Hollister Road (now out of business) disc brake kit. It uses rotors and calipers from a 2003 chevy HD2500. I have a m/c from a 1991 chevy 3500 with 4 wheel discs.
Will yours lock up the back brakes? It would take some research, maybe trial and error, to see if you need a better match between calipers and m/c. The bore of the m/c plays a big part in break pedal force to hydraulic pressure (aka caliper strength).
