Rear disc on A-body

11 3/4" Police/Taxi rotors up front with Firm Feel's brake pads. Rears are a Dr Diff Econo kit with a 2006 Mustang Cobra R rear disc and caliper with parking brake. Master cylinder is just under an inch in bore-size. No adjustable proportioning valve, as it doesn't need it. Possibly one of the best, most predictable brake set-ups I've ever driven on a Mopar. It is so good, that I am running the same set-up with a power booster on my E-Body. It doesn't need the power booster though, and makes the brakes a bit touchy.
What MC did you go with? Is it a disc/drum or disc/disc? If a disk/drum, did you remove the residual valve? Thanks