Had a guy I know bring his 1980 chevy 1/2 ton van down. It had a bad brake pull. The van had been into a garage a few times for this problem. Last time he had new calipers installed but it still did it.
So anyway we took the wheels off and found that the front brake hoses were plugged/restricted and the left one really bad.
What had happened is the metal clamp that goes around the hose and attaches it to the uppper control arm had started to rust. Over time as it rusted away it expanded and clamped down harder on the hose till it blocked it off.