MBM 4 wheel disc brake conversion master cylinder question

67Dart273 said

I used my stock 67 drum master on the 73/74 single piston brakes. I did poke a nail through the residual valves to rupture the valve. I have 4X wheel disc, they are as mentioned, front, and factory Lincoln Versailles rear (Ford 9")

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Where are the residual valves? I just changed my brakes from drum/drum to all disc also, and heard a late 90's caravan master would work good? Should I just keep the drum/drum mc and remove residual valves, or change master cylinders? And to what mc?