I was trying to clean this fuel tank up, but it's just too gunked up inside. My new plan is to flush it with water a few times, then cut it in half (on one side, right under where the strap goes), clean it manually, then weld it back together.

I'm thinking a big, slow, manual band saw will be the ticket, vertical or horizontal, whichever can cut a straight, clean line through the tank for me. Can anyone help me out with this?

And to answer any questions of "why don't you use a different tank?" it's because I don't want to. I'd rather try to restore this one.