I rebuilt a '84. The 110v system in the top half is simple stand alone system. Mine had 3 outlets and 2 over head lights. All these items were wire nutted together in the breaker box above the rear door. The system is powered by an extention cord that plugs into the outside drivers side fed outlet.
There is just a single piece of romex going from the line side of the breaker over the door to the outside male connector, nothing is dasiy chained,all the outlets and both lights have their own romex to the breaker box.
Mine is a 8' cabover, but drawings I have seen indicate all were wires similar. The location of the breaker box varied.
There is a sticky thread above that has a crude drawing.
Keith