Would I, no. Is it super dangerous, probably not. Here is a picture of a 1965 Ford B that was owned by a friend when it was rear ended by a semi in 1974. I ended up buying it and had a body shop put the body back together for our first real RV that isn't just tarps over a pickup truck. I did not put the tank back on the back. The inside was all ripped loose in the crash so I made the inside the way we wanted. The LP tank and tire took a lot of the impact. The LP tank was still sitting in the corner of my Dad's shop when we sold the place in January 2020 and was still holding propane.