I know this is an old thread but we now have a rear kit in the works soon to be available for 47-59 HO52 HO72 that has slide on drums. We have the test parts in, we will have to tweak them for the final version but it did allow us to do proof of concept. It will work on HO52 HO72 with slide on drums. It allows you to unbolt a rear brake assembly from a 2003 up to about 2010 2500HD and bolt it onto your stock rear end. It keeps the 2003 disc brake, parking brake and rotor without changing rear wheel track. You use your stock hub.
Here are a few pictures.
Rear disc swap
Rear Disc swap
It will be about 3- 4 weeks before its ready. But it is on the top of the work list for us. We do have a front kit and booster kit available now at
www.hollisterroad.com