What have you used for a replacement fuel tank

[entourageguy]

Hi everyone just found this site and looks great. Just purchased a 59 and have a question. What have people used as a replacement tank if moving from the cab? Filled mine up today and it is leaking by the small vent tube at tank. Drained off a few gallons
( or litres as it is called now up here) and it is ok. Looks like previous owner has put some kind of sealer around it. I would love to remove from cab but what is done if you put fuel cell under box floor? I think I saw a kit somewhere that puts a fuel door in the box bed.
Oh yea the rear bumper is gone and in it's place is a roll pan.