1970 Duster won’t stop.

My car had been sitting a year or 2 before I bought it. The previous owner said he never had an issue with them. I got the car running last week and went to back out of the garage. It took all I could do to get it to stop. Here are the details. Some might matter some might not. 4 speed car and the clutch pedal sits higher than the brake pedal. It is a disc drum setup with a power booster. Pedal pressure does not change when you start the car. Pedal does not drop when you start it. Pumping doesn’t do anything. Booster looks new. Rubber lines to calipers look fairly new. Where is ground zero to start on this thing. I do not think it was originally a disc brake car. Fluid is full.