This may seem like an over-simplification but if you're running a drum/drum system, a late 60's early 70's full sized GM master cylinder is what you want. It WILL have the built-in residual valves. It WILL fit the 3-1/2" hole pattern to mount the M/C to the (Chevy Duty) adaptor bracket.
Be sure to get the adaptors to plumb your lines into the M/C as they are not a direct plug-in.
If you are running a disc/drum system you could run a late 60's to early 70's Corvette disc/drum master and you would need to add the prop valve and a 2&10 pound residual valve.
These are the M/C's I'm currently running in my 54 truck which is on the road every day. I sure hope this helps you get started on your conversion.
Dave
