So, bit of back story. My 55 Wagon's brakes worked well. With the pedal about half way to the floor, I had full stopping power. One time, there was a pop/bang/noise and the pedal when to about 2 inches from the floor. The brakes still worked, and I drove it for a few weeks that way. I jacked up the truck and tested all 4 wheels and I was still able to spin the rear driver side tire by hand with the pedal to the floor. Once I disassembled that wheel, I found that they wheel cylinder wasn't hardly moving at all.
So, I replaced both rear wheel cylinders (and cleaned everything up) got everything back together and bled the lines with the vacuum bleeder...and.. was disappointed when the pedal still goes to the floor with zero resistance, and has basically no braking power, only enough to stop it from accidentally rolling out of the garage on its own.

Any thoughts on what my next move should be? I was thinking could be something inside the master cylinder. There are no leaks in the system as far as I can see, so I am not sure where else to go from here. Don't want to replace the master cylinder only to find out that it doesn't fix the issue either.

As an added bonus, I managed to snap one of the bleeder screws off the front wheel.
Ugh, guess I jinxed myself when I said I'd be driving it to work this week.

VTWilly