Here is the BAR webpage FAQ on bringing out of state vehicles into CA.
http://smogcheck.ca.gov/smogweb/Geninfo/default.asp?RefPage=/Geninfo/Publications/Out_of_State_Car_(Stop_Before_You_Buy).htm

From what I hear, they will look to see that the engine conversion has all the
stock components related to emissions as their guide. You also have to pass a
smog check for the emissions for either the vehicle year of manufacture or
engine year of manufacture - whichever is newer.

Kitzmann wrote:

> The smog check in California thing has me thinking.  I'm moving to CA next
> year and my van has a 1.8L conversion.  I'm wondering how many list members
> have conversions in CA and how much trouble they went through to get
> certified.  What about all the slightly modified components like airboxes
> and such?
>
> Dave K.