Ok, I have rebuilt the brakes on the F!. The primary issue was one of the bonded pads had torn off and was locking the right rear wheel when I hit the brakes. That should be a not issue now.
The new issue is the bleeding. I get good strong pressure out of the front brakes, with fluid shooting several inches out. The rear is not quite so good. The fluid shoots out, but not with a like pressure. The peddle is firm and at about 1/4 peddle. But, that is only after a couple pumps. If I let it set for a minute, the peddle will go almost to the floor.
I know this suggests air in the lines, but I am getting fluid, without any gurgling or bubbles, at all four. I have found no leaks in the line or any of the wheel cylinders. In fact, the only oddity I have found is the cap on the master. It's plastic. I know this was not original. Is it possible the PO had somehow sealed it and I have now broken that seal, causing my problem?
Is it possible to get a new cap without buying the whole master cylinder?
Any suggestions? Yeah I know, Keep pumping!

I did find a new, proper cap on Mac's. I have ordered it

 

Do you have discs or drums on the rear ? If drums it's quite likely that the shoes need to be adjusted .

 

Drums all around. But that's a great point. Properly adjusting the shoes, again, may be just what it needs.