Also, the Mopar adjustable proportioning valve mentioned in the second, unreadable pic is PN P5249088 which is reportedly adjustable from 100-1000 psi which should be adequate in dialing in the rears on a modded car-installed in the line going to the rears.

If you have an original combo valve that is rusted up internally which is pretty common on older valves, then you might consider one like this from Wilwood http://www.jegs.com/i/Wilwood/950/260-11179/10002/-1?parentProductId=1284815