I have the SSBC front 6 piston calipers and was going to upgrade the rear but they are out of business. So im looking for info on any OEM parts that can be used to increase the size of the rotors and larger 15% pistons to match the front. For the rotors it would need to work with the integrated parking drum and be around 14-15". The rotors are really key here and info seems to be lacking. once i find a rotor I can se if i can find any OEM calipers that use the same sized rotor with larger pistons. In the end I might just go with aftermarket calipers with real pistons. You can tell the truck is very front biased right now since the piston area went up around 18% with the front calipers. Im looking for an inexpensive way to better balance the truck and get the rear brakes to contribute more. Trucks tows heavy 80% of its time, this is a fun project with a little added safety. Fabrication of caliper brackets is not an issue.