In the late sixties and early seventies our big dealership here in Hartford - Grody Chevrolet - partnered with a couple local shops to custom install higher end radios and tape systems then were not available from the factory including the first generation of expensive cassette players in 1970. The base radios that were removed from a host of Impalas, Caprice, Estate wagons, Chevelle, Camaro & some vettes then were repackaged and sold over counter, used by sales to spruce up and sweeten baseline rides, or used as parts. I'm sure this practice was not unique to Grody.