1967 Barracuda 4 Speed 273 back fire issue

Starter not disengaging, engine not stopping at off, all point at the ignition switch or the wiring to/from it. I think it would hold systems hot and drain the battery too if this were the case. Hmmm... If it was mine I guess I would just dive into the wiring, taking my time to find and fix all of its faults. Anything that has been touched by previous owners is suspect in my mind too. If there is aftermarket radio, etc.. I undo all of their wiring and go back to stock configuration rather than spend time studying what they've done.