Stock pushrods?

 

They will work with stockers BUT id recommend at least our heavy duty 7.400 pushrods they are $65 shipped right now. (Today only)

 

so basically, moderate bolt-on mods will not affect emission/smog output so headers and cat-back shouldn't either. I suppose the only certainty would be if removing the cat' converters then?

 

Some states will have a visual inspection also and afaik headers (long tubes) wont pass but stories with carb sticker will.
Its basically all in the tune really and overall upkeep/condition of the vehicle.
Most bolt ons, properly tuned, wont affect emissions at all. Cams, you've gotta be a little more picky, but staying small or mild is a good bet itll pass.