65 dart vin

That number on the radiator support is the shipping order number and the last 5 digits will (or should) match the digits under the word "NUMBER" on the fender tag. To my knowledge no one is reproducing any kind of tag or plate with a VIN number on it - something about against Federal law. Your missing VIN tag is made out of stainless steel and is is about an inch or so by 2 to 3 inches and was secured with some kind of special glue. All 5 of my early A Bodies have the tag and no rivits holding the tag to the jamb.

I know from personal experience that a 65 broadcast sheet and fender tag do not provide VIN data. Only one place the VIN number was posted on the car...on the VIN tag located on the door jam. The radiator stamping likewise has nothing to do with the VIN.
Only course of action is a title search if you know any previous owners or apply for a new one.