On my 65 dart I went from non power 9" drums to 74 A discs/10" BBP (2&1/4"?) rear drums with a truck 1&1/8" (iirc) alum dual bowl MC & kept the OE splitter block & ran the forward bowl straight to the rear as Eberg touted but with no added adjustable prop valve & it performed flawless. It did lockup the rears first if I hit it hard and admittedly this was regular easy driving around town/no panic stops needed.
-people say you need the larger bowl half for the discs but for enthusiasts like ourselves who check the fluid level regularly the added insurance of a larger bowl ain't an absolute as it is not in danger of running dry like it might be with granny in a DD (liabilty issues for Ma) and on the MC bore dia people have had to stand on the pedal with a MC of too large a bore but I never ran into that and I dont think you will either in this case. IF you need a longer front flex hose the 78 Volare hose is longer & just cut off half of the metal bracket that is crimped in the middle of the hose (you'll see when you look at it).