Recently had a starter go bad on my 85 mustang. Its a 5.0 5 speed, carbureted with duraspark ignition. Replaced my starter and later found i also had a wiring issue that was causing a voltage drop. Fixed that issue and now having a problem when i turn the key to run position the car cranks over. Assumed bad solenoid but i had a spare known good part that I replaced it with, still having same problem. Any ideas where to look? Was after replacing ignition switch last year with a motorcraft replacement. Confirmed good battery, verified grounds. Could it be the tumbler itself? TIA