This kit is what we recommend to fully convert your 1971 Cougar over to LED Plasma exterior lights. Our WCCC brand LED lights are amongst the brightest on the market and have been specifically engineered with the nuances of the Mercury Cougar sequential system in mind. Keep in mind that over the years folks have become accustomed to very BRIGHT tail lights in traffic and the old incandescent bulbs are not only dim, but they take time to fully illuminate and a split second can make all the difference in stop and go traffic. Another reason to upgrade this system is that the reproduction turn signal switches are not as good as the originals and do not do well with the load of six incandescent bulbs. Even the original FoMoCo switches often failed prematurely in the Cougars. By reducing the load on the circuit to a fraction of factory specs, you will save yourself lots of time and money in repairs. Lastly... Cougar owners have always been rather proud of our unique sequential systems and by installing this system you will be pleasantly surprised at not only how intensely bright they are but how they illuminate a brilliant, true red that evenly radiates throughout the taillight cavity. The 1971 model year does require you to upgrade the unit in the trunk as well as the side markers. This kit includes the new sequential unit as well as the side marker adapters.