The pump shaft sticks out of the pump mounting flange a little. The pulley has a center hole/pilot hole that keeps the pulley centered on that shaft. If you do have a stick out shaft and a pilot hole in pulley, that part is a pretty tight fit. The bolt holes in the pulley need to be a bit larger than the bolt to compensate for tolerance. The shaft centers it, the bolts hold it on. That's a normal Chevy mount. What does "pulley off center" mean?
If you don't have what I describe, what do you have?
If holes don't line up, just hold pump tight and rotate the pulley until they do.
