Newer cars have an overrunning clutch type of pulley,this is so that if your alternator seizes while driving the vehicle the belt won't break.This almost never happens if the vehicle is driven daily or even weekly so the best advise i can give you if the car is a daily driver is to remove the plastic cap off of the front of the pulley and have it spot welded in 3 evenly spaced places.These pulley can cost over and above $300 and really do nothing to affect performance unless they are worn out.Cars ran since the twenties without them and they are just a cash cow in my mind,hope this helps.

There is no clutch on alternator. what they may have said that it needs rebuilt for the bearings in it are bad. rebuild or replace,