Help... Vin #'s dont match

They only are concerned with the #'s on the vin tag
and if the vin tag has been tampered with concealing
theft.
They won't understand why you are giving them incomplete #s taken from places on the car other than the tag.
i know. That's why i suggest running it online first for free, there's only a few options to fill the rest of the vin, we know its a duster. Therefore, run the thing online for the possibilities, if something comes up, then notify the cops, if not, run it, drive it and be happy. Or for piece of mind, talk to them anyway, tell them what you suspect but that has risks.