I have an old propane water heater with a fairly new main valve. I'd like to find a good used water heater but propane water heaters are rare. There are some 2 year old natural gas water heaters available and I'd like to know if there is a reason that I couldn't use my newish propane valve in a water heater that was originally set up for natural gas.

I'm assuming the burner assembly has a propane orfice so that would also be transfered.