The A12 is the package that introduced the 440 Six-Barrel to Plymouth (and its Dodge Super Bee A12 sibling) in mid-1969. Standout feature: a one-piece fiberglass lift-off hood with a flat-black finish and four chrome hood pins, the absence of wheel covers (steel wheels with chrome lugs only), and 15-inch wheels regardless of body. The package was sold both as Road Runner A12 and as Super Bee A12; identical mechanically, different badging.
By 1970 the lift-off hood was gone — the V-code Six-Pack used a regular hood with the scoop package. A12 specifically denotes the 1969 1/2 cars; later Six-Pack cars use V-code engine and the regular option callouts.