My 84 still has soft brakes... I honestly don't know what to do.

Initial problem:
Left front caliper was leaking out of one of the cylinders. This was the suspect cause of my soft pedal.

Action Taken:
Left front was replaced w/ rebuilt. At the same time, the 25 year old brake hoses showed cracking, so I replaced those too - fronts and rears.

Result:
Bled primary and secondary systems, no pedal pressure after the first system was bled or the second. The pedal is even worse now. Brake failure light does not come on until the pedal is all the way to the floor, so it seems both primary and secondary systems are holding consistent/equal pressures, they are just too low to work only triggering the failure light when they are on the floor.

Theory:
At this point, I'm suspecting a bad MC - I don't know what else it could be. The pressure differential warning block was rebuilt several years ago and it seems (from searching) fine. Also from what I've read, the rear pressure regulators that reduce pressure to the rear calipers and prevent rear wheel lock up will only fail if rusted through, that internal components rarely/do not go bad.