Today I re-adjusted all the brakes per the manual. Then I checked toe-board clearance and pedal freeplay. Both good. I used a Mighty-Vac to bleed the brakes again. Found it almost impossible to get any fluid out of any of them. Went around the whole car, then took it out for a drive. The brakes felt really crappy, then gradually started to improve. The more I drove, the better they got. The pulling on hard stops completely disappeared. Now I can hit the brakes, take my hands off the wheel, and it stays in a straight line. I was amazed at the improvement.
I think the seeping at the front wheels is the original bleeder screws, which I reused. I'll be replacing them tomorrow.


1956 Chevy 3200