Adding a mastercylinder to my 1935 P.U.

[Magic]

I am planing on upgrading my brake system on my 1935 pickup. By installing a dual master cylinder . And I am confused. I have been told both ways by people. Some say its better to use a smaller bore master cylinder,like a 11/16 bore. While others say I will have more brake pressure,using a bigger 1 1/8" bore master cylinder. Which is best ? Also I plan on installing inline residual pressure valves on the front and rear brake lines. And in installing them, which is best ? Installing them closer to the mastercylinder or as far away from it as possible,like closer to the wheelcylinders?