I have a 1984 500 SEC that was a grey market car. It came in through Long Island. These cars had made up vins. Mine has a plate riveted to the windshield post with a number embossed into the metal plate. This number too does not come up in any US computers including Dept of Motor Vehicles. Luckily, New York cars all have titles and I received a new title when I bought the car that says it is a 1984. That is sufficient for all of the things that I have had to do with the car. I would think your registration would do the same if you don't have a title.