any particular reason the stock location won't work? Is it because they don't want the tank in the cab with them. If they get in a bad enough wreck for that to become an issue they are very likely not going to be alive enough to worry about it. (just think about it a little bit) however if they want to move it for more room in the cab or something, that is another story. It is very possible the set up you are talking about may work, but there will be plenty of fab work involved most likely.