That's right – imagine that, back in the early 1970s, you could have been a good ecological citizen and checked the box for all the smog-reducing catalytic converters, charcoal canisters, reduced engine compression, and other gear that would keep the neighborhood kids from keeling over from carbon monoxide poisoning and/or carcinogenic hydrocarbon overdoses. Or, that you could have chosen the route of the flinty, hard-eyed individualist and thrown off the oppressive yoke of nanny-state Big Government, running a 14:1 compression V8 with a brace of fuel-dumping sidedraft Webers. By this time, the dirtiest engines would be fairly clean (by the standards of 40 years ago), though still way filthier than the requirements mandated by present-day rich-world governments.
So, which would it be for you? Pay extra for the hardware that makes your vehicle run clean and wear a halo, or go for the zero-smog-control package and wear horns? Explain your choice.