Only problem I see there is no pressure reduction to the rear brakes. Makes a panic stop a change your underwear experience. The pressure reduction prevents the rear brakes from locking up and the rear end becoming the front end. It allows the rear to immediately start applying but limits the rate the pressure goes up.
There's a youtube video that explains how the later prop valve for dual chamber master cylinders has a lot more to them than the setup you a using. There is also a shuttle valve that locks out either the front or rear brakes if either line breaks. It also synchronizes the brake application so the rear brakes start to apply before the front to also prevent spinouts.
I believe this was introduced 1968. The prop valve is the same for B and C bodies so they are available.
This video explains it very well:
It's for a GM but the Mopar design is the same.
This was the first step in brake engineering on the path to anti-lock systems.
