Pictured below are several pics of the original special water pump for use with the Model A & B Ford overhead valve cylinder head conversions sold under the Miller, Schofield, and Cragar names from the 1930's to the 1950's.
This original casting is cast iron, not aluminum.
The stock Model A water outlet bolts directly to the top of this pump casting, rather than to the cylinder head.
Another view. The pump mounts to the front face of the cylinder head, similar to a stock Model A water pump.
Though it is a four bolt pump, it has a different hole pattern than the stock Model A water pump.