Not mine but thought I would post for comment and on the very, very long shot this may be a unicorn part that came out of an R Model or belongs in an R Model or Trans Am coupe. The baffles inside the tank are very intriguing.
Jeff
https://lasvegas.craigslist.org/pts/d/las-vegas-very-rare-shelby-32-gal-gas/7683408840.html