California realizes that cars eventually need new components(including engines) and has come up with a pretty straight forward policy to address complete engine swaps as an option to a rebuild of the originally installed engine - see:

https://www.bar.ca.gov/Industry/Engi...uidelines.html

Key is:
"Make sure the engine and emission control configuration on exhaust-controlled vehicles are certified to the year of the vehicle or newer, and to the same or a more stringent new vehicle certification standard."

As such, an LS swap from a newer model California car should be fine in your Monte Carlo if you make it a complete swap with engine, transmission and ALL emissions components. Needs be a similar platform, i.e., newer passenger car like a Camaro, 1/2 ton Suburban, or SS Impala would be fine. A 3/4 ton truck - probably not so good.

If you want to read the entire California regulation (400 plus page!) on "Automotive Repair Dealers, Smog Check Stations and Technicians, Official Lamp and Brake Adjusting Stations and Adjusters", go to:
https://www.smogcheck.ca.gov/pdf/Law...g_20140718.pdf

As much as I despise the "people's republic of Oregon" we're still able to hot rod anything pre-1974 - at least for now.