Heh, 40 gallons is huge. I guess it would work though... like having a HUUUUUUGE bomb in the back of your truck. I don't think cops would try to pull me over if I had that in the back. I will try to figure something out then. I think when I go to rewire the truck I will put that bed cover (tonel, tonnel sp?) cover on it and then put the battery back there in the center and a mini tool box that you can't see unless you open the top on the bed. I would like to put a small box like that in there to put tools in it just in case.