1970 Cuda, 10-in rear drums, 11-in front rotors from a 1973 Dart. Manual disc/drum, and the Dart was also manual disc/drum.

My first question is about the prop valve ass'y, I got the valve ass'y from the Dart. It is (looks like) PV6070MOP.
In the Dart, apparently there was no metering "hold-off" valve. Please see pics. It seems to me the Dart had essentially
the same braking system I will be using, so why would one car need the metering valve ?

Second question is compatibility of the hydraulic parts. I need to buy a master cylinder, both front calipers, and both rear wheel cylinders.
Researching this, I'm leaning towards a 15/16 MC, 2.60-piston front calipers, 7/8-in rear cylinders.
I have 28" rear tires and 26" front tires.
Weight distribution: Car is a BB 4-speed 70 Cuda with power steering and battery back in the truck. 26" radiator, no A/C.

I'll probably go through Dr Diff for everything, including advice, but thought I would post here too.
Your advice and critique are much appreciated !