This grade "A" taillight harness will be a rare uncut beauty with nice looking plug ends and wiring. This unit is for Mercury Cougars built prior to 1-3-67 with the stop lamp relay positioned next to the sequential unit in the trunk as opposed to under dash found on models made after 1-2-67. XR7 and Standard Cougars use the same rear wiring harness to the taillights.
*NOTE* The stand out identifier of the early vs. late rear harness is the flat four prong plug with a red, two green and two black (male) wire. The late harness does not have this stop lamp relay plug next to the sequential plugs. No XR7 Cougars came equipped with this loom as the XR7 was not available until mid model year.
*NOTE* Need help diagnosing a Cougar turn signal problem? Victor Yarberry is the world's most knowledgeable expert on the subject. Vic has owned Cougars since the 1970's and is the designer of all of our solid state sequential systems. There is no question he cannot answer! Here is a link to a great source of information on the subject.