Alright, it turns out that a couple of wheel cylinders were stuck, plus the rear rubber line and the right front rubber line were completely stopped up. Maybe I'll have brakes on all 4 wheels again tomorrow afternoon. In all my years of working on cars, I have never seen this much stuff stopped up on an old car. I must have been lucky in the past. I get this finished, it will be time to tackle those door panels.

Glad you're making headway! I would go ahead and replace all four rubber lines while you are at it. The old lines will sponge in and out like bellows. This is a problem that is common but sometimes hard to identify.

glad you found the problem ! if replacing a couple of cylinders, replace them all. if the return springs are several [many ?] years old, you might consider those as well, and they aren't that much, cost wise. when you have the brakes apart, look closely at the backing plates for grooves, or worn depressions in the shoe contact pads. if any are found, a spot or two of weld, then ground down will fix that. small [tiny] depressions can be filed flat. upon reassembly, a dab of high temperature grease on these pads helps a lot.

I always replace everything from pedal to pads on anything questionable, or has been sitting for an unknown length of time.
Still finding everything over the counter.
That's the part that surprised me.
These systems are so easy I can do it in an afternoon or two.
I am no pro by a long shot.
No fancy lines and only a bender and flare kit for "special" tools.

These systems have lasted 40 years once and will do it again.
By then I will be long gone.

Brakes are fixed, even stops pretty straight from speed. Now to figure out a way of repairing the door panels because no one makes C body panels.