Can you get underneath and have a look around? You should see some steel support beams and then that will tell you where is the best place to put a large aquarium. There shouldn't be a problem with anything under a 75 gallon aquarium but if you are concerned I know someone that upgraded to a 210 tank I bought several corals from her Saltwater Corals
I am pretty sure it was a modular home or possibly a double wide. I haven't seen this particular tank but the other one was on an outside wall.