Factory build sheet discrepancy

Let me weigh in, There is a slim chance that something got goofed up along the way. Because the VIN, fender tag, and build sheet all say it was born with a slant 6, there is no way to prove otherwise. VIN#'s weren't stamped on engines until 1968 so that rules out the "numbers matching" argument. It is what it is. Build it and enjoy the ride.