Live in California, my car hasn't been registered since '04, no non op?

Your royally screwed.
Your going to have to pay 13 years of back registration, and penalty's if you want to register it in California in 2017, withought it ever being in the system as non op.
Another wrong response.
Once the car goes several years without being registered, it is dropped from the system. To register it now, it is as if the car never existed. There are no back fees to pay. You will need to get a VIN verification, pay transfer fees (Even though YOU are the last owner) and sales tax. I have bought "yard cars" that people bought and let sit for years. Almost every one of them was unregistered for10 years or more. EVERY time I called DMV to check status, they told me that the vehicle is no longer on file and will have to have a new file created.
It isn't as easy as re-registering but you are in no way screwed.