Hoping to get a little insight on a brake problem. I'm in need of a brake proportioning valve but, it's turning out to be a tad difficult finding the correct one. My 69 C10 is stock, no ones has messed with the brakes but for some reason I can't find the correct proportioning valve. I've purchased two from Classic Industries and both of them turned out to be the wrong one. They sent 5 port proportioning valves both times but I only have a 4 port... 2 inlet, 2 outlet factory 4 wheel drum. Is this such a difficult problem? Seems odd. Any advice would be greatly appreciated.