Frank,
The pulley clearly did not "just fall apart" when the fan bolts were removed. It was rusted or corroded on there pretty good. As soon as it was pressed, the holes all started to cave in, so we stopped.
Compared to the "new" water pump (with the narrow pulley) I bought, the old pulley seems like lighter grade metal, mounted onto a flat disk beneath. The newer pulley seemed like it was made of stouter metal, all one piece.
Not sure what that means. . .
I'm still confused about the pulley/belt size.
-Michael