look up the 831 thread in this section. There's a couple of us, including myself in the santa cruz/bay area. CA is pretty strict when it comes to non-USDM engines and smog is required every 2 years.
Check out this unofficial site:
California Smog Checks - Emissions Regulations, CA Smog Testing Stations - DMV Guide
and the official DMV site for california:
Smog Requirements
You may be able to get an LS1 or the usdm 2jz smog legal to drive on the roads, but i'm not sure. offroad is perfectly acceptable.