first... don't work with a srewdriver or something like that at the 'ears' of the pump! The pump is corroding at the outside and stucks then. The last one i removed came of after some days soaking in loads of WD40 and some help of a hot air gun.
I have somewhere seen a picture of a waterpump puller. They have clamped something around the pulley of the pump and work on that with a pull-hammer (sorry, i did not know the right word in english
)
I have the pics... somewhere.
If you send me your email adress by PM i will see if i can find them.
ciao Joachim
PS usually that is not good for the ball bearings, but i suppose you will change them, so...