It's a 66 with a single cylinder manual MC and 4 drums. Doesn't seem to have a proportioning valve, just a T with input line from the MC, two to the fronts, and one line to the rear brakes.

We started with the MC. Used a hand cranked pump to empty MC, cleaned, filled partially with new brake fluid and and pumped into a jar until clean. Then we bench bled on the car by running a clear plastic tube from where the brake line hooks up back up and into the MC. Things looked good.

Went to a rear wheel cylinder to start bleeding. There was a rubber hose from the bleeder screw going into a glass jar so we could see what was happening. At first the fluid flow was very slow - improved after cleaning bleeder screw. Kept bleeding the same wheel waiting for all of the old brake fluid to be flushed out by the new. Got clogged again, cleaned bleeder screw, still clogged, removed bleeder screw, pressed brake pedal, stuff came out, re-installed bleeder screw, went ok for a while. Tried pumping brakes with bleeder screw removed again - didn't help. Removed (ok, broke) brake line leading into wheel cylinder. Pressed pedal with the cylinder out of the picture - nothing.

Searched TC and read about Mity-Vacs and pressure bleeding. Removed the T (junction?) block on frame just under MC. Bled MC again - seems ok. Ran about 100 psi of air into the rear line at the junction block - nothing comes out of broken brake line by wheel cylinder.

Planning on disconnecting the T on the rear end that feeds the left and right wheel cylinders and trying to blow it out again, bypassing the left and right lines. Might try rigging up a pressure bleeder device.

Any suggestions?

Sounds like you've got a brake line replacement job in your future. With all the crud and breakage problems described I'd be inclined to work from the "major" joints in the system outward.

Major joints meaning the points where the main supply lines branch off to the devices at the wheels.

We'll try Classic Tube - good reviews.