Those were stock steel 14x6 wheels with an imitation plastic five spoke mag style full wheel cover. Though even back in 1967 only race cars wheels where made out of cast magnesium. Almost all of the popular aftermarket wheels were all cast out of aluminum after about 1962 (American offered a true mag as late as 1972).
And yes they were OEM from the dealer's store room. Chevy dealer installed optional equipment shown in the ad with the disclaimer in fine print at the bottom of the page.
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