If the vehicle was previously registered in California it should have already be taken to a California Smog Check Referee and had a BAR label affixed indicating the vehicle has had a legal engine change. If this vehicle is new to California or never been registered in California (or registered in California but the DMV and BAR never notified of the engine change; which would have been illegal and the inspecting smog station and owner subject to fines), then yes, you will need to have the smog referee inspect the engine change and "BAR" it... meaning the gas to diesel conversion has been done properly and the new engine does not pollute. Subsequent smog checks may be obtained at standard smog stations.
