RR, how did you address the single reservoir master cylinder?
When I converted my 65 Cuda to disc I used a later dual reservoir M/C and plumbing the brakes along with a prop valve wasn't real hard to do.
I will be switching to a dual reservoir set up. I already have the correct distribution block. I'll use all of the existing brake lines and add a new one for the additional reservoir. I expect I might have to replace the line to the block from the master cylinder.
I'll plan on the proportioning valve.