Re: Hot Water Heater Replacement in a mobile home.
Is there a difference between a "trailer" water heater and a standard residential water heater? Yes, it is a shiny sticker on the side that says "trailer rated", and the cost of this shiny sticker is a mere several hundred dollars. Is there a physical difference, no, not likely, however, if you choose to use a non-certified appliance in a trailer, you will nullify your insurance coverage, which you likely won't know about until it's too late. Your choice, just know that there are consequences.
As for a larger water heater, odds are that it won't be an issue as long as the existing floor and framing are sound. If there is any sponginess to the floor, I'd recommend opening it up and repairing it before installing the new water heater. In addition, if space is not an issue, then possibly moving the water heater where it is being fully supported by structure, and not just the cheap and cheesy particle board that trailer manufacturers love to use in everything.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!