I replaced one in a 2008 Allegro Bus with a 2 door 21 cu ft Kitchen Aid we got from Lowes. You can go to
A J Madison to get a good cut on all sizes and makes/models that are available. Their sorting engine is the best I found. Check the rear of your fridge compartment to see if some of the baffling can be removed. Tiffin had some in there to make the Norcold fit properly. I did have to lower the floor a couple of inches and also drop a CB panel under it but the fridge fit in the same width hole. Some folks are using Samsung counter depth units, but I got some unflattering info about Samsung product support and their high cost of controller boards in their refrigerators. That's why we went with a Kitchen Aid.
Good luck with your mod. What ever you choose, you'll wonder why you didn't do it sooner
Pigman & Piglady
2013 Tiffin Allegro Bus 43' QGP
2011 Chevy Silverado 1500
SMI Air Force One toad brake
Street Atlas USA Plus