Given the age of the vehicle there are numerous posibilities. The emergency brake cable may be sticking. The rear brake hoses may be swollen inside from age and causing the rear brakes to drag. The caliper pins may be sticking, but I would hope that whoever did the brakes would have replaced them, or at least greased them. A ciliper piston may be sticking. The rear wheel bearing(s) may be dry. There could also be a problem in the proportioning valve. Do some diagnostic work. | 
