smog vs. no smog

I have no idea what the smog laws are in other states, but I do have a good idea of them in CA.

If you put a '74 engine into a '93 car, it would have to pass the smog requirements for a '93 car of the same type(passenger, commercial). In fact, here in CA it is illegal to use an engine older than the car....if that makes any sense.

Actually, the initial question has a mistake in it. A PCV valve is considered "Smog Equipment" under today's rules and they've been around since, what, 1966? Seems I remember '66 was also the first year for Fuel Vapor canisters (in CA) - they're definitely smog equipment.

In 1980 to '87 I lived in Tucson and had to run my '73 Gran Torino through the annual smog checks. Once I figured out how to "de-tune" the ignition and carb so it would pass the test, it was no problem. Just "make it run like crap" for the test, put it back when I got home. Fortunately they only would put it on the "sniffer"; if they'd popped the hood on that California car, I'd spend a day or two explaining the million capped-off vacuum lines
No smog test here in Yuma; so I'm feeling much better about getting and keeping the Cougar (identical powertrain to the Torino) on the road

according to federal law, as i understand it, you can swap any engine into any car, you just have to maintain all the emission equipment that is required for the car. swapping a 302 from a 70 mustang into say an 85 grand marquis means you have to maintain the grand marquis' emission equipment. you then also have to deal with state laws as well. in california for example you cannot swap an older engine into a newer car, but if you want to swap a 5.0 engine from a 94 mustang, into say an 80 mustang, then you must install the engine emissions equipment from the 94 engine, and connect then, somehow, to the chassis emissions equipment of the 80 mustang. other states have their own requirements, and laws.