ELECTRICAL GREMLINS [OVERCHARGING 440-3]

Just a few comments to add here.
If yoiu haven't looked at this yet, it may (I hope) clarify how the grounded field terminal and idolated field terminal systems differ.
https://www.forabodiesonly.com/mopar/threads/identifying-chrysler-alternators-1960-1976.475691/
The year of the engine is not important. The vehicle year (and sometimes model and options) remains the same with respect to wiring.
Because its a motorhome, it may have been wired differently that the cars and regular trucks. It would be good to know if it was equiped with a second battery. If so, then we should figure out how that was wired in. There's been a few discussions in the past here (FABO) regarding auxilery batteries and how they get recharged.