Hey Buddy!!! another typical problem for a lot of us as i can see!!.. My car is still braking with only the front discs as i had the same problem... no pedal what so ever.... Back in the past when i was at it, i managed to make the car brake ok but the pedal resistance was NONE... softer than the clutch pedal.. awful...
I can make the story long but bottom line is my proportioning valve was broken... I bypassed it and the pedal inmediately got hard as a rock... The problem was that without it, the rear brakes blocked all the time and i had to disconect them in order to use the car... Now i have an adjustable rear brake preasure valve for the rear circuit that is waiting for me to attach somewere non visible (just to keep the looks as original as i can)
The front brakes are direct, full preasure and the prop valve is gone... Front brakes supposed to be 100% preasure as the rear ones much less... that is why i got an adjustable one...
Best of luck Buddy!