Trying to figure out brake problem with rear disc upgrade

[CreepinDeth]

I have a 1970 Olds 442 clone.
I took out the fake Olds 12 bolt 2.78 rear end, and put in a Chevy 12 Bolt Eaton Posi 3.73 I got off another member here earlier this year. It came with the Baer rear 11" disc setup. I have stock 10.75" factory front disc brakes.


I was told a 1979 Corvette Master with the 1 1/8" bore would be a great addition to make this system work. Plus an Adjustable Proportioning Valve for the rear. So far I've bled the system 5 - 6 times and I still have a mushy brake pedal. I put in a Fenco rebuilt 79 Vette master with 3/16" front and 1/4" rear lines. I'm not exactly sure if I need to upgrade to a 1" bore master cylinder, or if I'm doing something wrong here.

No matter what I have done, I still have an ultra mush pedal and I know I don't have any air left in there. I checked everywhere for leaks too, nothing. Something else has to be the problem. I was hoping maybe someone can help me figure it out. So far I've been told my rebuilt master COULD have bad seals, to order another. I just want to be sure what I'm putting in is going to really work. I've see other guys upgrade to rear discs with this master with no problems.

I have no idea if this Baer brake setup uses a big or little piston and how I should calculate this all out. I'm stabbing in the dark here.