Booster upgrade and Prop Valve

I am swapping a 1996 XJ brake booster, master cylinder into my 1990 XJ. I have found lots of good info reading past posts on this site. I am still confused on one issue. Am I correct in assuming I can use either the original proportioning valve or the newer one from the 1996? I realize there are plumbing issues with the fitting sizes - metric vs. SAE threads, but is either one acceptable from a performance/safety issue ?

Thanks
DanDXJ

Only the master is metric thread (12x1.0 & 10x1.0), the prop valve is standard thread. I would get the stock master lines from the 96+ that go from the master to the prop valve. That way everything is going to work the first time. But yes the stock prop valve from the 90 should work without any issue.