Proportioning Valve

I need a source for a proportioning valve. I swapped in the front discs from a 75 A body (large bolt pattern) but have the stock proportioning valve for my 72 that came stock with front discs/rear drums.

A bodies in wrecking yards around here are EXTREMELY rare. I'm in the Reno, NV area.

Any help would be appreciated.

Thanks,

fastmopar