Engine stays running without key in ignition (and more!)

This post shows how the isolated field alternator works with its regulator.
Identifying Chrysler Alternators (1960-1976)


Because the regulator has boot type connector, voltage it is sensing will have to be the next closest locations in the J2 circuit.
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Voltage of the J2 circuit should be fairly close to the votlage measured at the alternator output and the battery at hte same time.
If there is a big difference, then that indicates resistance to current flow.