Combination valve problems

That is a strange situation. You know, most of the prop valves that mopar made were all the same. A 4dr was the same as a 2 dr, And even a pickup truck was the same. So, if it were me, I would find one from a pickup truck from the 80's or early 90's. Actually, they really do not do that much. They are more like a delay valve than a proportioning valve. even if you ran without one, I'll bet you wouldn't know much different un less you were doing some very extreme braking and even then you could just go to some smaller diameter wheel cylinders in the rear to make the bias correct. I think maybe the wildwood adjustable prop valve would have been a better choice though. They just delay the rear brakes from locking up before the fronts lockup. this prevents a spin out. Good article for adapting abs to older cars in the mopar action mag of the last few months. This would be the real way to prevent skidding. All the parts are in the J-yard. One thing though, you have to make sure that all the parts are working together correctly and that the system is totally bleed right and that the drum brakes are adjusted right. Everything has to be right and double check everything. You must use the correct master cylinder and the rod and pedal must be right. Double check all the basics first. This is all I can tell you for know without more information. (I might get some flack from some of this advice on the prop valve though).