1968 Dart Brake and Booster issues?

Pics of the Set-UP?

I'll try and get by the mechanics in the next few days to take a picture. I live downtown and don't have access to a garage where I can have a car in pieces, so I have ended up farming out work these days. The aftermarket P.Valve was plumbed in like the old D.Valve and worked fine for a few months but then things seemed to go very Flintstone Brakes. I parked it for winter/Covid when I saw the leaking etc. I pulled it out of storage to get the tranny rebuilt this Fall and decided to tackle the annoying leaky brake setup at the same time. I sort of thought I had been sold a leaky junk unit and why not go back to having a crude warning light system? I thought swapping out the 4 wheel drum MCylinder for a Disc/Drum MC would mean I could go back to my old DValve. I suppose I would likely need that NOS style P.Valve to solve the problem though?