hate to re hash such an old post...
but does anybody have any conclusions on this as to what they found works best?
I am looking to replace all the lines on my 86 and want to do away with the non operable rear valve...
I was going to throw a simple T block in there and just be done with it and upgrade my proportion valve once I decide on a rear end brake setup (drums or disks)
if you're redoing all the lines just go get an XJ proportioning valve and do it. You'll ditch the rear valve and the third "saftey" line completely. It's a much cleaner option.
while you're at it, consider going disk brakes in the rear and use a ZJ valve. Disk brake swap is trivial. You unbolt your backing plates, bolt new ones on.
Finding the parts is the biggest headache. Of course there's also the 8.8 option.