THe emissions equipment, Lean Burn, smog pumps, etc. can lead to lower emissions, but have the drawbacks of reduced driveablility, expense, and lower overall performance. Depending on your local laws, you may have to put all of that stuff back, or you may not have to, as long as you can pass the emissions tests without them. The anti-pollution equipment is removed by most for good reason, it isn't just because hot rodders don't like it. Smog pumps take power ro run, Lean Burn systems make for rough running cars, even when factory new. Today, most Lean Burn systems are not running properly, either due to the electronics module itself going bad, or some of the associated parts going bad due to aging. There really isn't anybody who can repair the modules, for example, and also no demand because everybody removed the Lean Burn system anyway. WIthout a fully functional Lean Burs system (which would somewhat play the part of the vacuum and mechanical advance mechanisms) you have a fixed advance (static only) distributor. You can't tap into the vacuum advance port on the carburetor, as there isn't one. So, most people get a carb with a distributor vacuum port, a distributor with both mechanical and vacuum advances, and the standard Mopar Ignition Control Module (pre-1976), ballast resistor, and a coil, and duplicate the pre-Lean Burn carburetor/ignition system. Generally speaking, it works out really well.
As for how clean it runs, you need to keep in mind that the factories doe not individually tune up each and every car though the aseempbly line. They did used to do a basic tune (set basic static timing), and rely on the design to make it work the rest of the way. I don't think they do anything besides start the engine and check for codes on today's cars. A properly tuned up plder car can be made to run fairly cleanly and efficiently if things are looked after properly. Whether or not it meets your local emissions requirements or regulations is really dependent on what your local regulations are. In many places, cars older than 20 years are not tested for emissions, or are only subject to sniffer (exhaut gas analyser in the tail pipe) tests. Other places want to see all of the factory emssions equipment in place; most of the time, this consists of checking to see if the catalytic converter is in place, as the people doing the visual inspection don't know what they are looking at inside the engine compartment. In other places, registering the car as a special interest/collector car means no inspection required (where I live).
Kostas
