Rust in the drums can cause this. Instead of your shoes sliding to a stop they grab right away on the rusty drum inside surface. Take the front drums off and if they are rusty inside clean them up with sand paper. Put them back on and if it still does it I'm with Merv, rebuild. Something that many people neglect with there classic cars is the brake fluid. Every few years it should be completely replaced. Totally bled out. If you don't you are going to need to rebuild the system.