As pictured, I have a 6 blade solid fan for sale. It has slotted holes so it should fit the hub on either the early short water pumps or the later (1969 and newer) long water pumps.
Measuring across the two blades that are pretty much opposite each other I get about 18 1/2".
I have no idea what it came from originally, I've had it forever. Looks to be in good shape other than a good clean and repaint would be nice.