Catalytic converters
As others have said, 1975 was the first year they could have had a cat as that’s when they modified the floor pan under the drivers seat to fit the cat. No A bodies before 1974 had a cat. However, not all A bodies in 1975 had cats, mine is a 1975 and did not have a cat; that could be a Canada only thing though. Perhaps some States didn’t require a cat so it could be hit and miss depending on which state the car was sold new in.