1957 Chevrolet passenger car water pump

[nomad]

Part no. 3736493 a correct one for a 1957 Chevrolet should not have the top hole drilled and tapped into the casting . Is that correct ? Also it appears that the truck water pumps have a different size tapped outlet hole from the passenger cars ? Bill mock appears to have sold out to (Chevy Cool ) . Hopefully they may have some answers ?

[nomad]

The trucks had the top boss on the water pumps drilled and tapped for the Hydromantic transmission's . Also the water pumps with a " T " and a date code were from engines built in the "Towonda " plant and the 57 Chevrolet water pumps with no " T "and no date codes were build in the " Flint " engine plant .