Mr. Hoyt;
This is the way early vehicles were built and how the operator monitored the charging system. This worked well for decades until "idiot lights" were used instead. Rarely was the charging circuit fused, but there were/are devices for that.
It also works the same today unless someone adds equipment (like A/C) where it (orginal) no longer can, due to the added power source/drain.
The "hall effect" devices have been used by mechanics to test charging systems W/O ammeters for decades. The one shown is not needed as a Voltmeter allows the operator to monitor charging safely. It's just another 'gadget'.
M;
You WILL need to make other modifications to do that on your 48. Stick with a Generator or use an early GM (30A) Alternator and the (orginal) wiring design is just fine.
Happy trails.
