I was thinking of dual tanks myself. I cut the fuel door and neck
out of a wrecked suburban. Since you are dealing with a TF, you might want to take a look at that approach. Barring finding an original, you could look for a more modern vehicle for your fuel doors and get a matched pair. If you are using a new tank, you can cut and weld on it with no problem. I wouldn't put any heat on a used than, though.
Another thought is that any parts house that supplies over-the-road trucking will have both mechanical and electrical fuel tank selectors. The electric ones switch the gauge, too.
Best wishes,
Les
