The right master cylinder.

Call Cass @DoctorDiff . But I'd be running one of his 15/16" m/c's. I have one on my Duster and my Challenger, both manual disks. The challenger has 11.75" rotors and 11x2.5" drums and the duster has 13" rotors and PBR calipers (dr diff kit) and 11x2.5" drums. Works great on both cars.

With 4 wheel disks you should also plan on an adjustable prop valve if you don't already have one.