To get a more specific answer, identify what "original Norcold" you have. We don't all know how each and every RV was equipped!
There are three key measures of what fits. Obviously the opening has to be wide enough & tall enough, but depth is also a concern. RV fridges are shallow, so "cabinet depth" residential units are sometimes necessary so they don't stick out too far. Finally, sufficient space for the door(s) to swing out and/or drawer to open is needed. That's mostly determined by what is opposite the fridge location. Once you determine the size and style of fridge that fits in the space you have, you then need to figure out how to get it inside the coach. It may go through the entry door if fully stripped down, but sometimes a window or even a windshield has to be removed.
Just what works best in your coach will depend on the interior layout and what fridge you now have. Get out that tape measure and go to work!
I replaced a Norcold 1200 with a GE 14.5 cu ft top freezer model, standard depth. The controlling factor for my install was the door opening swing. I had room for a wider and taller fridge, but was short on depth & swing because there was a pull-out pantry across the aisle from the fridge.