Try these sites. the second link has other links - Mac's Antique Auto Parts looks like a good source. There's also a guy who has old Ford Motor corp die castings and actually recreates new parts from the old molds, Dennis Carpenter.
I'm not much of a mechanic - I have friends that love to do this kind of stuff - I just like to drive em, so I can't be much help other than to share the research I've done on the web.
Don't know your location but try Stan the Ford Man in Washington state, he may have some gas tanks...his phone number is 360-687-1216....he advertises parts in the Galaxie Club magazine for 59-68 Galaxies.
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