I have had countless problems with my 74 duster and I m located in the OC area. So I may be able to help. I have gone through 2 bulk heads bc that red power wire melts the plastic big mess. Since you have replaced the ignition switch it sounds like what ever is powering your run may also be powering your off. I would start at the bulk head since thats where your problem starts and use a test light and see where the power is coming from. I m not sure on your car which color the wires are but thats a start
