Pretty good idea for the VIN check. However, I don't know how many of the older cars we're interested in would be a part of this database.
The National Insurance Crime Bureau (NICB) has access to a database of vehicles which were reported as stolen within the past five years and remain unrecovered or declared as salvage.
As you say, maybe - maybe not.
Personally, I'd like to see a VIN database of every pre-1975 Dodge and Plymouth muscle car. Of course, that would mean visiting junkyards, barns, back yards, etc. But it sure would be nice to have! Plunk in a VIN and see if it's on the street
...or... rusting away as "yard art."