Major brake issues, help please

[88Stanger]

I have been fighting a brake issue for far to long. I have little to no pressure at the rear, here is what i have and here is what i have tried:

1969 C10 complete rebuild from ground up with LS conversion
all new brake lines installed, front to rear
Disc conversion on Front and Rear
new POL Wilwood power booster, dual master cylinder and Disc to Disc prop valve

I am trying to bleed the brakes and the rear bleeders have only a small amount of fluid coming out, with little to no pressure. This is after an hour of bleeding the brakes the good ole way with buddy on the brakes and me bleeding.
The master cylinder does have the plug installed where the warning light goes
no leaks to date

i have checked the distance the rod is extending from the booster when the brakes are depressed fully. there is full travel on the brake pedal also

i did pre-bleed the master cylinder also with a bleeder kit

So thats where i am. I am just frustrated. i have searched and tried what i know of so far other than connecting the rear line directly to the master cylinder and seeing what pressure i have then. i do have an adjustable prop. valve from SSBC valve that i also plan to try after the direct connection.
I am open to any and all ideas at this point.
Thanks in advance for any help.