when did catalytic converters start?

74-75 was sort of a transition period based on where the car was sold, and the exact engine combo. Pretty much all cars in 76 and most light trucks in 79.

Running a cat shouldn't be a big deal if your A/F ratio is reasonable and you burn more gas than oil. Yeah, it's one more part, but they do a LOT to clean up unburned hydrocarbons. New cats aren't particularly restrictive either. The worst cat now is light years better than the best cat then.