The NOS 1979-1993 Ford Mustang 2.3L 4 cyl rocker arm D8FZ-6564-A is a genuine Ford part designed specifically for the Mustang models mentioned. This rocker arm is a crucial component in the valvetrain system of the engine, ensuring proper functionality of the engine's timing and performance. As a new old stock (NOS) item, this part is in excellent condition and ready to install, providing a reliable and high-quality replacement option for Ford Mustang owners.bb23