Pulleys have their own unique V-spacing and must use original 1971-1982 brackets and water pump.Increases horsepower by reducing accessory drag. 12-15 h.p. at rear wheels typical.Eliminates belt throwing. Designed for daily street driving. Precision CNC machined to run perfectly true. 6061-T6 aluminum for extra strength and wear. Finished with a “No Polishing” clear powdercoat.