I acquired a 1976 ford f150 4x4 flat bed truck a few years back, been working on it since it got in my garage, so far motor rebuilt (360), tranny gone thru, all new everything front end wise, new drive shafts, rust removal and paint of frame (most of it), anyway, I am down to brakes, as stated, all new up front, but rear wouldn't bleed, so from research figured it was my proportional valve, it was stuck rearward, found the reason, 2 leaks on crossover line from years ago, so I figured I would attempt to "reset" the proportional valve, is didn't reset, so I removed the proportion valve, it is frozen bad. So I am looking for a new one, cant seem to find one with the proper line sizes, I hear Ford used these valves on multiple vehicles so does anyone know what will fit and what wont. The vehicle has disk in front, drum in rear, does anyone out there have one for sale or can guide me in a direction to get one?? Please advise.

 

I believe a proportioning valve only notifies the operator of a difference in line pressures usually due to a leak.
You might be able to obtain some adapter fittings to use the only valve you can get.. I have been able to get the necessary fittings from a local NAPA store. You might take the valve to them and see what they can do to allow you to use it.
Pretty sure you will need to go from std fitting to metric if the valve is for something after 1981 0r 82.