1965 Barracuda Formula S with factory air near St Louis

999 was a paint code for a non-standard paint (ie. Playboy Playmate pink cars were all 999) but stripe was just an option, sometimes dealer applied and not "S" specific. Few things were uniquely "S" only, but tach is a good indicator. "S" was a package option. I think you could almost option out a non 'S' to an 'S'....tach may have been unique.