In 1967, Plymouth introduced the GTX as the trim-level for their mid-size Belvedere. Positioned as the "gentlemen's hot rod," the GTX came standard with the Commando 440 cubic inch big block with the 426 cubic inch Hemi as the only optional engine.

Creates a considerably hotter spark that lets the flame expand more rapidly in the combustion chamber and a more complete and efficient burn of the air/fuel mixture