Never heard of such a thing as "some late 68's" invoices were lost. Sounds like the seller is trying to make up a story because it might not be a 400 car, however, Pontiac started stamping blocks with a partial VIN in 1968, so I would think that if the block VIN matches the vehicle VIN, and it's a 400, that's a probable 400 car. Of course, people restamp blocks, etc., but at least this is the first step.
