help with rear brake issue 72 cheyenne

[zicc1835]

well i thought i had a booster issue because my brakes did not perform as good as my stepside with no booster. so i replaced that when i separated the master cylinder i saw some fluid come out the back i replaced the MC i tried to bleed the rear brakes by pumping and holding down nothing but some drips coming out ...i thought i would gravity bleed the rears nothing but drops. i took the line off the back of the valve(red circle )and open one rear bleeder at a time and got the fluid to squirt out both sides one at a time when i put air to it... so to me no kinks or flattened line either side or any where ....i bought a new proportioning valve still can't get rears to bleed ...i took that line(red circle) off the back of the new valve for the rear brakes pushed the peddle down no fluid comes out the back of the new valve. fronts bleed fine ....took it out for a ride and stomped on the peddle a few times no change ...im not getting any fluid thru the valve to the rear brakes????? I believe my rear brakes have not been engaging at all since i started driving it a few months ago.... so I'm a dummy with all new parts ...thanks for any help