The B in the pad means it is a 66 motor , A is 65. As for the numbers matching the vin, I doubt the factory worried about that at all.They used what was available . Generally if it's within 3 months of the build date it's what it came with.
Ok cool. The car was build February (11th I think) so about a month difference. That’s pretty cool how they did things back then. Thanks for the info valiantwagonguy.