I also have realized that it appears that I have the master cylinder for the 11" rear brakes installed on my truck even though my truck has 13" brakes.... could this be causing the rear brake issue??
Its been hell trying to get these rear brakes working. Who ever owned the truck before me never used the rear brakes. Fronts work great, but the parking brake didnt work because someone adjusted it to max trying to fix the underlying hydraulic issue. I replaced the shoes and wheel cylinders...