The 1967-73 Mercury Cougars are considered the “true” Cougars that shared their platform with their Mustang cousins.  Sharing architecture with the Mustang, the Cougars had a longer wheelbase, featured more luxurious appointments, more formal styling, and the 427 ci big block that was not available in its Ford counterpart.  The early cougars featured sequential turn signals and 1967-70 models featured distinctive hidden headlights.