4 wheel disc on 74 Duster - Prop valve?

Don' know what to tell ya. Sounds like a master/ bleeding / plugged problem, not so much a "parts" problem

I (was until paint shop jail) run 73 /4 front Duster brakes, and rear Linc Versailles disk, with NO prop valve, only the original 67 warning switch. I even run the old original drum master---just punctured the residual valves. Stops perfect