Getting the Hemi meant that the car would get 15 inch rims, but the highly desireable Kelsey Hayes cast center styled wheels were recalled for being lemons, forever after known as the "Recall Wheels" They broke under normal use. So?
So they looked around at what they could do to make it look half decent, for a 15 inch steel plain rim, and voila. Right out of the parts bin. The Deluxe hub cap.
and the trivia is from this months Muscle Car Review letters to the editor, from John Shoe, August issue, 2017, page 8