I DID NOT replace my Norcold 1211 with a residential frig. I felt (for me) the cutting framing and finish work required was not something I would feel good doing.
So dw and I put a new cooling unit in from JC Refrigeration
https://jc-refrigeration.com/
We did however put the strictly 120v unit in as we are always plugged in. To exchange the unit was a very easy project. Limited tools need, very good help from JC. The cost of the unit was a little under 1000.00. I can not say how easy installing a dual unit would be, but it sure can not be any harder than what we did. The new unit runs at setting 4 keeps the frig a 30 and the freezer at 5.
You may want to think about this way.
Good Luck safe travels