Kirk, regardless of the way
you think of the information, I believe you'll find that any jurisdiction has a line on the title labeled "vehicle identification number", spelled out or abbreviated, capitalized or lower cased, and depending on the year of manufacture and year of title issuance, that identification number might be the original engine number, or what GM called a "vehicle number"
in the era discussed [but you call "build tag #'s and Letters" for some reason, although GM called it a "serial number plate"], or the modern federal government defined "VIN" ... all good, we pretty much know what's being discussed whether it's called a vin, a VIN, or a serial number
Bill