what cars used the prop valve that will work with the 68 Kelsey-Hayes dis brake setup on a 68 Dart GTS? i have a 68 slant 6 dart in the backyard with manual drums. would that be the same valve? thanks!!

I would say most likely 67-72 A bodies w the kh discs. your 4 wheel drum 68 would only have a T splitter and not a prop valve.

The 73-76 prop/combo valve is a direct fit into the 68 for use with any factory disc brakes, including the K-H. I am not positive, but I think 68 was like 67 and used a separate valve in the rear brake line just behind the distribution block.