Hello Bob.
Thanks for your reply. This is a 2 element water heater and assuming that the most likely damaging forces would be verticle (ie, bumps in the road). Since the elements are mounted into the side of the tank, laying the tank on it’s side with the element covers pointing up would make them less vulnerable. Just a thought. Everyone I know of that has a pick-up, has a camper shell on it, making it impossible to stand the water heater upright.
Alvin