This sounds like a problem I had with a 68 Olds. The brakes were hard and would lock up one drum. After burning out a couple sets of brake pads (not to mention the drum), I found that I had TWO problems.
Problem #1. I used a power brake master cylinder with a non-power brake car "because a bigger master cylinder had to be good" right? wrong.
Problem #2. One of my brake hoses had degraded on the inside, a flap of rubber was acting like a one way valve, fluid would go in to the brake cylinder, then the little flap would block the fluid from returning!
I replaced the brake hoses and put my original master cylinder back on, and the brakes worked great!
