brake proportioning valve
 

Does anybody know what the difference between the 69 proportioning valve with front drum brakes and 71 with front disc is. Will the 69 with drums work if I convert to 72 disc.

There is definately a difference between disc and drum as far as the proportioning valve is concerned. The drum unit has a residual valve that maintains some pressure on the wheel cylinders. The disc does not need or want that pressure.