1976 and newer vehicles in CA must pass smog inspections to renew registration (every other year) and when selling vehicle (seller's responsibility). If you plan to do an engine swap or any modification, I would urge you to do your research beforehand. An engine from a donor vehicle must be from same year or newer and of a similar size and configuration as what would have been originally available. And all of the emmissions related equipment etc from the donor vehicle. ( the smog referee would like to see the VIN from the donor and essentially you will need to comply with emmission standards of the donor vehicle).There are e-rod engines that are CARB compliant so that's an option. I have a 1985 Monte Carlo with a 4.3 V6. I was considering a swap to a 350 but a 350 was never offered in that year, only 305, so I'm not sure. (Sure, externally they look the same but if they check engine numbers or VIN of donor...)These are just a few examples, there is a lot to be researched. I'm just saying, I've seen a lot of threads where guys want to do, this, that and the other thing, but a word of caution. Do your homework if you're in CA. Make sure any aftermarket stuff like exhaust systems or even air cleaners are CARB compliant. I recently had to replace a catalytic converter and shopping online for a stock replacement I learned that there are those for federal compliance and those that are CARB compliant. When they do a smog check they look under the car for the converter and if it's been replaced they will look for the number stamped on it that indicates it's the correct one and compliant. By the way the CARB compliant cat for my car was 4 times as expensive as the federal one. Anyway if you have a pre 1975 car you will not have these concerns. I have a 73 Dodge Dart and a 67 Impala and smog inspections are not required so I guess I can do pretty much any reasonable modification without much worry.