Master cylinder

Not for me; I have a drill and a box of bits. If you wreck it, thennnnn it would be easiest to remedy it, by replacing it..
I haven't seen a drum/drum car with a Proportioning valve. A Junction block?yes. Or a junction block with a Safety switch? yes. Those I have seen.
If you are running 295s out back, you probably don't need a P-valve. Even with 275s my 68 Barracuda didn't need it. I still have a brand new valve here that I bought for the car, in the planning stage. After the roadtest, I decided she didn't need it so I am running without one.It stops real nice.