1975 was the first year for catalytic converters.
Back then no-one could pronounce “catalytic,” so everyone seemed to call them “Cadillac converters.” We had a 1977 Chevrolet equipped with one, and it never converted into a Cadillac.
One can’t forget the joys of early car emission controls, and engines that would run on after you turned off the ignition. My friend had a Mustang II, it ran almost as well with the ignition off as it did with the ignition on. What a piece of crap!