Replacing a 16 gal Water Heater with On Demand

[High5er]

Hey all. We bought a new 5th wheel last October and need to change our 16 gallon water heater over to a tankless/on-demand heater. Before people start telling my why I shouldn't, I've already made up my mind. We had one on our last trailer and know what we're getting into.

My question is this: Has anyone done this on their own trailer? Specifically replacing a tank this size. The opening is huge (I will need an 18 inch door). I ultimately want to get a 60k BTU or better and need to find a manufacturer who can cover that size of door.

I'm sure Truma has something, but we're looking at having to pack up and drag our house to the dealer then shell out $2500 for the unit and installation. I'm hoping I can get some recommendations for one I can install in an afternoon on my own.