90 XJ brake proportioning valve

I have determined my lack of brake pressure to the rear cylinders to be a fault proportioning valve. Now the problem is finding one. The factory P/N for a '90 XJ is 5200 6221 and for an '87-'89 is 5200 0097. The '90 XJ P/N in not available from the dealer. I pulled a proportioning valve from an '88 XJ today at the junkyard just as a backup, but I am not sure it will work for me. Does anyone know the differance between years? There were quite a few mid-90 XJ's at the junkyard the seemed to have the same looking proportioning valve body as my '90 XJ (maybe the guts are different due to different rear brakes/axles?). Can the 90 be cross referenced against a GM P/N or against a new XJ? Thanks!

Checked Summit for adjustable proportionate valves?

If you remove the switch on top of the valve and try to move the internal valve over to

where it goes with a tiny pick, maybe it will restore flow to the rear.

How did you remove your PV without destroying your brake lines?

My 89 brake lines wouldn't budge when I tried to take mine out.

I have not checked Summit, but seeing that a new OEM part may be hard to come by, I may not have an option.

I have not removed the old one, but I am guessing the lines are going to be very difficult to remove since they have been on there for 23 years. I had to cut the lines on the one I pulled from the junkyard. Did not try removing the top switch, but I took the front fitting off (bleeder valve??) then removed/reinstalled the valve and bled the system. Don't think it fixed my problem, though, but I figured I'd try the simple stuff first. Did not think about removing the top switch.