Sidelight:
Before the Fifties, most American luxury car manufacturers did a lively business in custom-made hearses, ambulances, flower cars, etc. And/or, they made their chassis available to custom coachwork companies like LeBaron to be made into specialty cars for wealthy individuals. But by the mid-Fifties, Cadillac had so dominated the luxury car business that they were the only suppliers of those custom-made vehicles. Chrysler maintained a connection with Carrozeria Ghia of Turin Italy for "dream cars"--one-offs shown at automobile expos. But Ghia did produce a few of those Crown Imperials for individuals.

Another sidelight: Truman was the last President to use a Packard. Ike was a Cad-man all the way. JFK preferred Lincoln, as did LBJ.