Check the dimensions on the furnace and stay as close to original as possible to make installation easy. My guess would be the NT 16 would be a drop in with the intake/exhaust fitting pretty easily.
As for the fridge, Dometic has a chart that tells what current models can be used for replacement of the old timers. If you are using the old cabinet this will save you some time and effort, but don't expect to install without any trouble at all. Chart:
Looks like a 2351 is the closest replacement for an RM 46. I have one of these in my Minuet and it works like a charm. I had to do some fitting and filling to make it fit.