Plymouth needed an answer to the Pontiac GTO, and in 1967 they built one by dropping a standard 440-cubic-inch, 375-horsepower Super Commando V8 into a dressed-up Belvedere and calling it the GTX. Unlike most muscle cars of the era, buyers didn’t have to option their way up to big power – Plymouth handed it to them standard, with the fabled 426 Hemi waiting as an upgrade.