Why do you want to move it? I think if I relocated it I would add saddle tanks between the frame and running board apron (available as a kit). Someone makes a kit to do what you are trying to do on Model A passenger cars that I assume would work on the trucks. Remember that Ford added reinforcements to their frame because the weight of the tank caused the frames crack. You would probably have better luck getting your answer on HAMB, http://www.jalopyjournal.com/forum/forums/the-hokey-***-message-board.5/ , or reachable from the "Hot Roads and Customs" Forum on this site.
Charlie Stephens