Catalytic converters

72bluNblu said

It may still be illegal to defeat or remove a catalytic converter on a 1975 vehicle if it came with one originally, but if you're not ever required to have a smog test or inspection on that vehicle, I don't know how anyone would find out.

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A smog tech told me that owners are supposed to retain all emission equipment that are installed on pollution controlled vehicles, even if they are exempt from testing.
In short, your 1975 car is required by law to have a converter but they don't require inspections to validate compliance.

So make sure you follow the law.