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IIRC, 74 or 75 was the first year for the supercab/extended cab trucks. I know there weren't any pre-73 ones. I have seen custom made extended cabs, but it takes a lot of work.
I don't know where you got that date, according to the Standard Catalog, June of 74 was the introduction of the supercab (Ford's term for the two door extended cab), and from everything else I can find, 65 was the first year Ford offered a factory crew cab, before that you could custom-order one from an aftermarket coach company.