Correct me if I am wrong, but didn't Chevy move the tank from behind the seat, to behind the cab in 1973? Which also caused some to catch on fire from side collisions. I believe that there was a recall of some sort because of lawsuits. I think it was regarding the tank being outside the frame rails. Which only provided sheet metal as a buffer during a collision.
If that is all correct (which I think it is), if you decide to move it out of the cab, you had probably better to try and keep it between the frame rails also. That could be difficult, as I don't think that there is a lot of room.
As I said earlier, under the seat works for me. So long as you don't have any leaks, I don't see why to bother with moving it.
