WHAT IS THE DIFFERENCE BETWEEN A CHEVY SHORT WATER PUMP AND A LONG WATER PUMP?

The following information was found in our Edelbrock catalog.
The difference is the length of the hub. Chevrolet used a short water pump on small block passenger car engines from 1955-68, 1969-70 350 Corvettes, and 1955-72 light duty trucks. The dimension from the engine block surface to the water pump hub is 5 5/8". The pilot shaft diameter is 5/8". Long water pumps were used on small block passenger cars engines from 1969-87 and on 1973-86 light duty trucks. The dimension from the block surface to the hub is 6 15/16". The pilot shaft diameter is also 5/8". However, 1971-82 Corvettes have a short water pump with a larger 3/4" pilot shaft. Do not mix and match pulleys from short and long water pump engines because this will cause pulley misalignment. If you can fit your hand between the water pump and the block, You have a long style water pump.