Took the fan off to paint and noticed a crack. Got a NOS fan blade and it did not match. The part # on this fan is correct. The existing fan has a 1" hole and uses 1/4" bolts. The new fan has 5/8" center hole. The new fan is 2" larger in diameter. Tried to get the old pulley off to check for #s or see if pump flanged has two sets of screw holes - could not get off. Pulley appears to have center cap that protrudes out and you can see a 5/8" shaft end inside it. What do I have existing here? The existing fan has 4 rivets new one two.