Re: proportioning valve
Take the valve out of the system, take it apart and clean it. After verifying the shutoff valve moves in the bore, the make a tool from a spare brake fitting that screws into the switch port and the butt end of a 1/8 drill bit. Center the valve manually, screw in the fitting, slide in the drill bit to seat in the valve then glue the bit in place in the fitting. Re-install the valve and bleed the system. Remove the tool and install the switch and harness.
Nest time you bleed or work on the system, remove the switch first and install the tool to hold the valve in place.
You can check with Master Power or Stainless Steel to see if there are replacement valves, otherwise you'll have to source one from a similar scrapped car.
1967 Falcon 4 door 351C - 70 Mustang 351C
Owner built, owner abused.