Mustang 8.8 rear disc

Hello,
Can you try to bleed (just a test) by loosing the line that goes from the body into the rubber hose that goes to the rear diff.
This way if you get no pressure (little fluid) you know its forward of the rear. Then try at the out put of proportioning valve feeding the rear and see the results. You can also check at the output of the master (to the rear) and see.
Check that you have complete travel of the rod going into the master and the piston in the master is not sticking.
You should also remove the bleeders at the calipers to see if there clogged.
Keep us up to date on your findings.
Happy Mopar :) (and ford's i guess LOL)
Arron