1966 valiant dual master distribution block

Magnum, Pishta, those look like they are just distribution blocks. Did you also have a proportioning valve plumbed in?
Our 65 got some Kelsey Hays disks we pulled off our 67 vert when we did drilled 4 wheel disks. The K-H disks with rear drums works great with no prop valve, good balance running rear drums. We have adjustable valves but typically only use them on disk/disk set ups for better balance during serious braking.