GM offerd their first factory crew cabs in '73, as Oldsub states. Anything before would have been aftermarket, although, GMC did make a hanfull of what one could call a "crew cab" in the early '30s. But these were not pickups, but custom order tractor tailor trucks.
International had a crew cab truck at least as far back as '54, they also produced a crew cab truck with a very short bed at that time, the Travellette (and the autoamkers think they came up with something new! HA! )
