Your 1979-93 Mustang's accessory drive plays a huge role in your engine's operation. Adding a set of underdrive pulleys, a/c delete, or a replacement harmonic balancer can increase the power in your Fox Body by reducing weight and strain on the engine not to mention proper tuning with better timing marks you can actually see. Got an alternator that is going out? Pick up a replacement offered in different amperage to satisfy your electrical needs. Top it off with a new tensioner and serpentine belt to prevent belt slippage or failure.