1976 was the year that pollution control crap was mandated for cars ... downhill from there ...
The 1970’s was the perfect storm for cars. We had the gas crunch, 5mph bumper mandates, and pollution controls. On Ed’s Auto Reviews he has a recent video where he goes over the catastrophic effect the 5mph bumpers had (like the Ford-style battering-ram bumpers that could down a tank).
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.