What’s the exact process to identify a real 66 Formula S Barracuda?

1967 was the last year for the 273 four barrel...

Years ago, while at Duke Tufty Dodge in Sioux Falls SD, my parts man noticed the 1968 Parts Manual listed the 273 H/Perf. engine code for the VIN same as 1967, and here it is in my 1968 Parts Manual. Not an argument, just an interesting quirk.

68 VIN Engine Codes.JPG