I was told our fridge was factory installed before walls and roof were added to our 1973 Class A. It failed 10 years back and the new unit was 2.5" wider than the door - yet we still got it through!
To replace it, the door frame had to be removed first. That widened the door opening, but the fridge was still an inch too wide. Then we laid the fridge on its back. The fridge had a lip/frame extending outward from the front face of the unit all the way around about 1/2" or so. That lip fit flat against the surface of the wall around the perimeter of the opening in the wall when the fridge was installed in the opening.
With the fridge on its back, the lip projected out flat to either side of the fridge. The body of the fridge behind the lip was just slightly narrower than the lip - small enough to fit through the door opening (with some pushing help), and we only had to cut a 1/8" high, 1/2" deep, notch into either side of the wall of the door opening. The fridge was then inserted through the opening, with the lip of the fridge sliding through the notches on either side. The door frame was then replaced and that covered up most of the notches we'd cut - the remainder was filled with silicone of a matching color.