Which Master Cylinder to use?

Just converted my 68 Barracuda to front 73+ disc brakes and keeping drums in the rear. When i bought the car it had drums all around, but a disc/drum master cylinder so I do not believe it will have a residual valve built into it. I want to use power brakes, so my question is, what master cylinder/booster do i get for this set up? do any come with RPVs built in? and then will the Proportioning Valve come before or after the factory distribution block(brake light switch)? thank you all in advance! still not sure what cam i will be using so that i can run power brakes so any advice on that too would be great. It is a 340 with x heads 10:1 and I am running a 4 speed