During the past eighteen plus years I have purchased many vehicles, cars and light trucks in various states, Alabama, South Dakota, and Montana, to name a few, which I brought to California.
In every instance, if I purchased vehicles that were not licensed/titled, i.e., had license plates, registration and a title I had problems getting a clear CA title, etc.
I have had several vehicles that had notarized Bill of Sales in lieu of a title, etc., in all cases the state DMV would not accept the notarized Bill of Sale because the notarized Bill of Sale only indentify's the person that signed the Bill of Sale..
My advise would to contact the local DMV office, asked them what they will accept as legal documents of ownership for out of state vehicles..
As a general rule they will require that the vehicle have license plates, even if they are expired, registration, a clear title, and that the serial number on the vehicle match the numbers shown on the paper work.
In most instances, a number on the engine don't work, the DMV will want the serial number that is stamped into the frame/chassis or is attached to body via rivets, etc.
I generall arm myself with info from the Standard Catalog of American Cars, which shows the location and number sequence for vehicle ID numbers.