Thinderbird Gas tank

Almost all the major auto parts stores carry tanks for this era of car, they are aftermarket, usually made by brands like Spectra. You can also find them listed on Ebay and Amazon too. If you want something more performance rated, check the speed catalogs like Summit, Jegs, etc. If you want NOS (new old stock) check specialty parts makers for classic Fords. There are too many of these to list, but NOS tanks are not that hard to find. I prefer to buy "better than original" performance parts from aftermarket speed catalogs, you'll get more bang for your buck. Only go the NOS route if you're doing a faithful or concourse restoration. Plenty of TBird forums out there to steer you to aftermarket parts, you might also find a forum member with an original tank they're willing to part with.