I'm not sure how the classic car companies deal with this in their rating programs, for those of us in the more standard world we don't have data pre-'81 on VINs so a non-issue. But then, we don't really want this type of car any way. For what I do, our data is very good on cars straight from the factory. The older a car gets, the less likely it will be similar to what came out of the factory.