This aluminum version of orvette style?water pump was originally used on 1971-82 small block Chevrolet Corvettes but is now used throughout the motorsports industry. Pump is built using all new components and an aluminum body for added weight savings over original cast iron pumps. Pump features a 3/4' main shaft and bearings with a 3/4' pilot and a billet steel hub that has a set screw retainer for use on higher RPM applications. Block mount to fan hub dimension is 5-13/16'.