1991 chevy 1500 water pump removal

im in the process of replacing the exhaust manifold gaskets on a chevy 1500. there is a bracket that attaches to the manifold, rear of the alternator and the back of the water pump. the only way (that i can see) to remove the bracket it to remove the water pump.
The source of fustration at the moment it the bolt on the fron of the water pump pullie that needs to be taken out so that the pillie can be taken off to get at the bolts to remove that water pump (just a little confusing eh?)

any way, the answer i want to get at is if the water pump pullie os crimped or pressed onto the bolt/shaft in the center, because as many diffrient ways i try to loosen the bolt (impact gun, allen key, tapping it to losen rust) it just seels to strip the bolt further (the bolt in question is a 3/8' allen socket)

hepl is very much apricaited)