These premium springs are made using high quality spring steel to assure a smooth stable ride that will last for years. They will also help lift that sagging rear end. Ford originally listed more than 24 different springs for the Mustang between 1964-1973. The parts varied only slightly, depending on body style, options, engine size, handling options, and transmission. Scott Drake has chosen 2 different springs as the most universal and one of these should meet most customers' needs. This spring is the the more heavy duty of the 2 stock applications. May raise car above original stock height depending on total weight of vehicle. This is especially true on early model 6cyl cars. Features O.E.M. style clamps, correct "hot cupped" ends, anti-squeak pads, front eye bushing installed and O.E.M. 4 leaf design. Light Duty version is sold under part number C5ZZ-5560-S.