This pump is for use with an engine that is turning 7000 RPM plus. It can also be used on the street in a hot climate. The small outlet to the head has been modified having a screw in plug so you can do away with this outlet. the impellers have only 3 vanes vs 6 of a standard pump. The reason of only 3 is that at a high RPM the pump will cavitate thus causing overheating. This modification has been done for many years with the stock car guys. These are new aluminum water pumps - not used ones.
Water Pump - Competition - "A" Series