Legal Question in Civil Litigation in California

If the seller won't deliver, the only option right now is a lawsuit either for possession of the car or recovery of your $40K.

Mr. Mickelson is right, assuming that the seller took your money (and assuming $40K is the amount you agreed to pay, which is not how I read your question). My sense is that the seller backed out of the deal before any money changed hands. If that is what happened, then you will probably only be able to recover the difference between what the car is worth and what the seller agreed to accept for it. That sum may not be worth suing over, especially since you do not live locally.

Note that I have presumed you and the seller made a valid contract. It sounds like you did, but you might not have.