Our 5th wheel has a partial generator prep package, but it does NOT have the generator box in the basement. Rather, it has a 4 pole 50 amp twist-lock Marinco receptacle on the front of the 5th wheel adjacent to the front compartment door. This allows me to run 2 each Yamaha EF2000is generators in parallel in the bed of the pickup to power one of our 15000 BTU A/Cs to precool the 5th wheel while we're traveling. Living in Texas, that works for us.
Rusty