Valve question
WHAT MODEL YEAR is your original car, and I assume it has drum brakes?
The valve pictured IS NOT a proportioning valve. It is quite simply a distribution block with the warning light switch. The switch consists of a simple piston which is normally centered, with the switch OFF. IF one "end" or the other loses pressure, the piston "shuttles" to one side, triggering the switch.
This thread:
http://www.forabodiesonly.com/mopar/showthread.php?t=134889
The photos below clearly show that at least some cars use SEPARATE prop. valves I found one drawing that seems to indicate that some cars used a 1 switch, 2 a metering valve, and 3 a prop valve in the same car.
These drawings are out of the 67 and 69 shop manuals:
Out of the 70 shop manual: