The body stamps are legal identifiers, they are what law enforcement uses to determine VIN fraud cases like dash VIN swaps.
They also use them to determine the original full VIN if it is missing, this is why you see some state issued VINs with the full original VIN as part of the full state issued VIN.
They also know how to check for welds around the numbers using forensics.
As a secondary identifier the body stamps are relevant. If there is an issue with the dash VIN then yeah, they look at body stamps. But what do they look at with pre 68 cars? Or how about even older ones where the engine serial number is the VIN and it has a swapped engine?
Best bet is to talk to the relevant authorities first and save yourself some grief and money.
