disc swap, prop. valve and mastr cyl

[veltex]

I am gathering parts for a disc swap, I have a 68 power drum c20 set up now, switching to a 71-72 c20 power disc set up have a-arms, b-joints, spindles, rotors & caliprs, main link, still need to round up tie rod ends , master cylinder and prop valve. Where is the best place to get this stuff? Booster will still work right? Why are new prop valves so pricey? thanks