There is so much idle speculation in some of these responses that providing sound counsel is difficult. Prior to our current VIN system many cars were registered/titled with many different combinations of numbers including engine number(very popular), body number, construed combinations (such as offered by the OP) or even the full chassis number. To be considerate of your heirs, or even of yourself if you think you might sell the car during your lifetime, it would behoove you to contact your state's DMV (or equivalent) and inquire about what is necessary to correct an identification number. This will usually require a personal inspection by a DMV inspector or member of the state police, but if your documents are in order a new registration/title sporting the proper numbers will be quickly issued. Since you, not your wife, girlfriend, or children, know more about your car's history than anyone else, I urge you confront this task immediately. If you don't, at the time of sale either the lawyer's fees will be huge to correct the title or the proceeds will be greatly reduced due to the numeric inconsistency.