Chevrolet, Ford, Cadillac, Lincoln and Desoto were big advertisers in National Geographic in the fifties.
Sorry, I'm not a NG expert, but I do watch for Chevy stuff on the web.
Here's what I'm aware of from Chevrolet's "1 USA" ads in NG in 57. There were ads in the Feb thru July issues --that I know of...
Had to reduce to post...