If you are running the Coyote engine and purchase the FFR alternator kit you will receive a Motorcraft belt tensioner and will need to replace the pulley on it with the six rib pulley that comes with the kit. It is useful to know that the pulley bolt has a LEFT HAND THREAD and turns clockwise for removal. If you fracture the bolt not knowing this, you may have to buy a replacement tensioner unit as the bolt is not available from Ford spares. I did it and know that at least here in Australia Hex head M10 x 25mm left hand threaded bolts are an extinct species. Strangely enough though you can readily buy left hand thread M10 nuts anywhere!