Previously only available with inline-six and small-block V8 power, the Mustang gained a 390-cubic-inch (6.4-liter) V8 in 1967. The S-code four-barrel units came with 320 horsepower and 427 pound ...

It improved on 427 and 428 big-block engines with ... However, just a few years later, the 1967 model year Mustang 390 GT was already lagging behind competing muscle cars from Chrysler and GM.