I did exactly what you are talking about. I gutted/converted a Norcold into an old ice box. If you go to my web site (see below), then go to our cruising prep pages and our projects. I put in a number of photos.
The company that made my superinsulation may not be able to do the same now.
After all of this time, our Norcold may be failing. I know it is using more power than it did (when running) when we put it in.
If I was starting from scratch now, I would NOT build it in. What I would do (no matter what) is build a shelf in the galley
sized to hold one of the Norcold or Engel units on. That way, when (not if) is goes bad, or they come out with some new super unit that uses on 0.1 Amp to freez 100 Lbs of meat, you can just swap out the old unit.
Hope this helps.