There was a member here that posted about having their gas tank redone by them a couple of years ago. He said that when he got it back that it looked like new. He said that it costed him a pretty penny to have his tank redone as he had to ship it to them then pay for the restoration and return shipping. They claim to be able to repair and restore any tank in any condition.
made one out of SS ,pretty easy fab,welded the sending ring to the top.the hardest part was finding a ss 1.25 tube for the fuel hose to hook to. A sheet metal fab shop should be able to copy the old tank. 4 breaks on the main body and 2 side panels, a little welding BadaBingBadaBOOM it works!!!! good luck