I have 'dual' 50A shore power receptacles on my 5th wheel. One front left side just under overhang and one rear left side.
Originally used a auto transfer switch...both feeds came into switch then leads went out to main AC Dist Panel.
Transfer switch failed, replacement failed upon install.....mfg. stated "Could you ship those back to us we are having issues"
I installed a 125A sub-panel in basement compartment. Both feed into sub-panel and have dual pole 5A breakers for each feed which are mechanically interlocked so only one set can be closed at a time.
Self contained generator in bed of truck with 50A twist lock plug (30A service)
Can plug into front or rear.
Can plug trailer shore power into front or rear--depends on where power pedestal is located.
Then just flip that set of breakers to ON
Been using this set up for 7 yrs.
Had to get the sub-panel
3 large junction boxes--One for each set of wires from receptacles and one for wires to main panel
15' of #6 wire in red/black/white/green for wiring from front receptacle to junction box
50A Marinco receptacle for front
30' of #6 wire in red/black/white/green for 3 10' runs from sub-panel to the 3 junction boxes
2 double pole 50A breaker sets
Front Recpt----------junction box.........to sub-panel/breaker
Rear Recpt-----------junction box.........to sub-panel/breaker
Main feed from sub-panel---------junction box.......OEM main to AC Dist Panel