The 1986 16' Scamp I bought had the original reefer removed and replaced with a dorm fridge.
I replaced that with a Norcold 12/120 marine refrigerator. The power supply converts the 12 volt DC to 18 volt AC for the swing compressor and a part of the circuitry has a relay to switch the 12 volts to the oscillator. I used this to power a small 12 volt computer style fan mounted below the rear coils to improve the cooling.
The original cutouts for the fridge I filled in with fiberglass removed from the Scamp bulkheads I no longer used.
The fridge is built into the space by the door to the rear about 2 ft wide. The sides are plywood bulkheads to reinforce the shell on the street side.
Since the refrigerator needed to be higher for better access this left room for added venting from the bottom.
the top is vented behind the microwave
On my trailer every space provided through the shell leaked and the floor was rotted in these areas.
When I removed the belly band I also found that there were a few unsealed holes found.
The water heater access was filled in as well and was replaced with a tankless unit on the tongue.
My goal with my camper is to have it sealed and water tight and critter and bug free.
There is currently no propane
inside the camper and the A/C is a split unit with no place for water or bugs it get inside.
I just hope it works as I envision it.