There are MANY water pumps. I have at least six different variants upstairs in my barn as a kind of display of variation.
To my knowledge Only Model A era Ford pumps include the brass pressure tight alemite fitting (brass cap) and the alemite front bearing fitting.
Ford did experiment a bit with the pumps along the way. Came to me from a parts box was a pump which had the standard shaft/impeller/gland, but the front nose of the pump was "small" and contained only a brass (very worn out) bushing. It did have grease fitting both front and rear and other than the non-roller bearing front was identical to Ford. As you have found, this design was not Ford's best.
Some pumps appearing similar to the Model A have NO gland nut - these may have been provided by Ford after the onset of the V8 engine as they have the same impeller as the two V8 pumps used in the V8. These usually have only a front grease fitting as the rear is "self sealing and lubricating" like their V8 cousin.
But a whole gamut of other aftermarket pumps exist.
Were this mine, I would source a casting from Ebay, and build up a pump more in the conventional Ford design.
See Vince Falter's comments on pump repop parts at
http://www.fordgarage.com/pages/waterpumpshafts.htm
There is more interesting information on water pumps (and most everything else Model A) at Vince's site.
www.fordgarage.com
Joe K