Period LIFE magazine photo below along with a comprehensive 1956 Mechanix Illustrated article, accurately shows anatomy of a concept car; all auto design manufacturing companies today follow the exact same time honored concept car business platform and/or blueprint. 

From the first family of Automobile Design 

Other articles can be found further down. One by Hugh Humphrey, editor of Car Life magazine titled Design-Unlimited along with CUE, a New Yorker style magazine. These articles help unravel more archival evidence. 

Notice how this quote that's on page 54 of the Car Life magazine article, below, properly locates and credits an artist to his historic works of art, "Most of his own work is conducted in a tiny, black-out office which bears a fictitious name on its door. Here he (Earl) concocts the GM experimental cars which later evolve into the dreamboats like Cadillac’s LaEspada, Oldsmobile’s F-88, Buick’s Wildcat, Pontiac’s Bonneville Special, ad Strato-Streak, and the popular Chevrolet Corvette." 

Below, January 15, 1949 issue of CUE magazine with article  "Meet the G. M. Designer"  by Bogart Rogers