Some of these engines get upgraded to serpentine belt drive, so tension loads have to be considered very carefully. It’s not as simple as hanging a much larger alternator or a second one on engine. If not done right, belt can slip, or it could overload other components. Some of the initial kits to add second alternators on various engines ran into this problem. Mercedes, for example, offers a kit for the Sprinter diesel but places limits to maintain proper performance and reliability.
We digress. Back to future electric motorhomes, not old ones.