First thing know what you need to know... Forget the Federal regulation requiring imported car to be at least 25 years old. This only exempts the auto from federal safety regulation.

• California Air Resources Board - Grey Market Cars Here is a outline:
  • 1967 model year vehicles and older: No testing required
  • 1968 model year to 1974 model year vehicles: California does not recommend the purchase or importation of these years of NON-USA vehicles, even if currently registered in another state.
  • 1975 model year vehicles to the present: (EXCLUDING any vehicle obtained by a California resident within two years of its date of production) require a "Certificate of Conformance" issued by the ARB after a successful laboratory test.
  • Diesel vehicles: 1979 model year and older vehicles with original-equipment diesel engines are exempt from Direct Import lab testing requirements.