HogBeast, I would strongly advise against attempting to register a non-USDM diesel in California. They have made it essentially impossible without going through California Environmental Engineering in Santa Ana (or whatever the Norcal equivalent is). All new registrations are sent through CARB's office, and they will flag a non-standard VIN and send you a rejection letter, regardless of whatever the person at the DMV does or doesn't do. My experience has been that the DMV and CARB aren't great at communicating with one another. It's also unclear if they're even allowing JDM/EDM/ADM diesels here, even with CEE mods...
Sam80, the out-of-state registration exemption no longer applies, and the language related to it has been removed from the DMV and CARB websites. Unfortunately, regardless of where the VIN is verified or who does it, non-standard VINs now get flagged by CARB and rejected. AAA doesn't have a clue and doesn't know what to do with new registrations that aren't completely vanilla and cookie-cutter (ask me how I know...). Even small-town DMVs won't work now: Even if they give you the green light at the field office, they'll still send it to Sacramento, where it'll get sent to CARB, who will reject it.
The only viable option now is the old out-of-state registration trick in Montana, SD, etc. For whatever reason, non-USDM diesels suffered a major crackdown a few years ago and are no longer allowed.