I mounted mine in an enclosure made with an angle iron frame and 18 ga. panels (louvered on sides) except for the bottom, which is 12 ga. My generator doesn't weigh that much though. I made an exhaust extension that goes out the back and turns down. It is bolted to the floor supports, My bus is a Wayne body and has C-shaped supports so this was pretty easy. I also screwed it to the body on the outside. I retained the panel cut from the outside as an access door, just hinged it on top and put latches on the bottom. The 8 inches below that I covered with an expanded metal screen for air flow. The floor supports will support the weight with no problem if they are in good condition. The frame is really too far inboard to mount to unless you brace all of the way across to the other side to cantilever the weight. I will post pictures soon.
79 International Wayne