gas tank

[51350]

Just getting ready to assemble frame on my 52 short box, I want to keep my spare under the back. Any body have suggestions on tanks between frame and driveshaft, I want to put one each side and join together with one filler have only got about 10 -11inches height & width but can get about 3ft long. If I have to can get them made of aluminum close by just thought somebody might have simpler and cheaper idea.