Sounds like a starter relay stuck shut? There's a starter relay under the dash. I think it's called a magnetic switch in the parts diagrams. If it has welded itself shut, it will try to drive the starter regardless of the switch position.
Your ignition switch energizes the coil in the starter relay which pulls the contactor together, sending juice to the starter. Has nothing to do with the V/R, the starter/generator or the ignition switch. To check this, check for continuity across the relay (between two big terminals) with no power applied to the small terminals. If there is continuity, that's the problem, If it's open (infinite resistance) then check it again with 12v applied to the small terminals. It should close and show continuity (no resistance/zero ohms).
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