Look at Posts #8 and #9 in this Tread.
https://www.montanaowners.com/forums...ad.php?t=86634
Someone I know mounted two female receptacles of the back wall of the pass-thru compartment. One is connected to the rear power supply and the other is connected to your new front power wiring. They then added a male plug to the wiring from the power panel that they plug manually into the appropriate power supply source (rear or front).
Try doing a Search for "manual transfer" or "transfer switch" and you might find other solutions.