Brake effort will be high with the large diameter master cylinder. So you'll need to stand on the pedal to get the car to stop. If you want a lower pedal effort and don't mind more pedal travel then swap to a smaller bore size in the master cylinder.

The drum distribution block with a rear mounted prop valve should work just fine. That is a standard way to go when retrofitting an older car. My '65 is set up the same way.

Only thing you should double check is your caliper mounting. If you rear mounted a set of front mounted calipers then you might have installed them upside down. People do that all the time and then they can't figure out why the brakes don't work very well. The bleeder needs to be at the very top of the caliper so that air can escape.