I don't know of any way to mount a solid fan on a threaded pump. You may need to bite the bullet, and either get another clutch-type fan from a salvage yard, or new one from a parts store.
Either that, or get an older water pump and V-belt pully to use the solid mount fan.
I'm not sure when the threaded hub/clutch came into use, but non-a/c trucks didn't use it until well after the a/c equipped ones, as they usually got a solid mount fan.

 

ya im goin to go to the junkyard sat. does anyone know of a place that would sell factory fans

 

How did it go 8525ford?