The 67 Dart is having problems with getting no power at all at times. It will start and run great most of the time then sometimes I turn the key and get nothing. I changed the starter relay and it has a new battery all the conections are good. Do you think it is the wire coming throught the firewall rusting out or the igintion switch? It is driving me nuts trying to figure it out and the guy comes next week to pick it up.