Here's what a $2 Ford repair manual which I came across said about flathead water pumps:

     How to overhaul water pumps: 1939-40 Models: The water pump used on 60H.P. engine (Fig.8) is held in the engine block by threads that are machined on the pump body which is screwed directly into the port in front end of the engine block.  This pump can be used on either the right or the left side of the engine.  To take the pump apart for the installation of new parts, remove the rubber cap 9, pull the impeller spring 2 out, unhook the spring retained 6, let go into the shaft and remove the impeller and spring form the other end of the shaft.  Press pulley off the front end of the impeller shaft, pry retainer spring 7 out of its recess and remove the impeller shaft and bearing assembly 5 from the front end of the pump body.  Caution: Always replace the rubber dust cap on the front end of the fan pulley hub.
     The water pumps used on the 85 H.P. and 95 H.P. and Mercury engines bolted to the front end of the cylinder block.  There are two pumps used, one right and one left.  The impeller and shaft ssembly is held in the pump body by the fanpulley which is held on the end of the impeller shaft by a tight press fit.  To take these pumps apart to install new parts, press the impeller shaft out of the fan pulley and remove the parts.  The seal, when greased will slip over the shaft much more easily.  The pump used on 85 H.P. passenger car engines is shown dismantled in Fig.9.  The heavy duty type pump used on 85 H.P. and 95 H.P. truck engines is shown dismantled in Fig. 10. Note: The impeller shaft must be removed from the rear of the pump body for passenger and commercial cars (shown in Fig. 9), and form the front of the pump for heavy duty truck pumps (shown in Fig. 10).