[351wStang]

Must have an open ground somewhere in the wiring. Something is giving the starter a constant signal. My car did the same thing but was fine after I replaced the solenoid. I would start by going over all connections and making sure they are tight and clean. After that run 1 wire at a time, one may be skinned somewhere and you just havent seen it when replacing parts. If you have a testlight you may be able to find a wire that goes hot with the key in START position and is supposed to be dead when the key is in the RUN position, but that stays hot instead. That would tell you either you switch never broke the connection between start and run or the wire is getting juice from something else that goes hot when the key is on. Thats all I know to tell you. Hope I didnt confuse you. Sounds like you have tryed the simple things, now it gets time consuming. Best of luck to you though. Let me know if there is anything else I can do. Hope this helps.