I have a Motor's heavy truck manual with a little information about that alternator, but no clear schematics showing how it's wired with a mechanical regulator. It does mention that there's a relay used to energize the alternator on startup. If the relay has been eliminated, it's possible there's a back-feed to the ignition circuit that would keep it running on shutdown. The regulator you picture does not look like an original-equipment Delco item, and it might be wired somewhat differently internally. The transistorized regulator used with that alternator was much more common, and it only had a 3-wire connector, with the regulator base grounded to the body metal. I ran one on a 64 White Freightliner, set up for positive ground.
Jerry
