Trans Dapt Performance Products Chrome Crankshaft pulleys are solid steel construction, and have a durable Chrome finish. One, two and three groove pulleys are available for both long and short water pump applications. The bolt circle diameter on short water pump pulley is 1.75", and 2.30" on long water pump pulleys. Chevrolet has made a variety of pulley diameters. Trans Dapt has chosen to use the most popular diameter for their pulleys. In some cases, the stock accessories may not run at exactly the same speed as originally designed. Although Corvettes have a short water pump through 1982, our short water pump pulleys will fit 55-74 only. NOTE: Due to the various casting configurations on aftermarket water pumps (especially aluminum pumps), exact fit can not be guaranteed on all applications.