MBM 4 wheel disc brake conversion master cylinder question

The difference "generally" between drum and disc masters is:

Older drum cylinders had same size front/ rear reservoirs, this is not a big deal
Newer drum cylinders had off size reservoirs "I guess" because they were case in "disc" era
Disc cylinders do NOT have residual pressure valves for the disc section. Generally all drum masters have residual valves

Size: Larger piston gives you more difficult braking effort, but less pedal movement
Smaller of course, opposite