On a 16 year old car, these things are bound to happen, though rare. It could be just that due to metal fatigue, one of the rivets has come lose or fallen off.
Your best bet is using the regular pulley, unless you want to run any other thing off your fan-belt.
You would best be advised to take a sample of your pulley in, as a sample, to buy the replacement, in case there have been any modifications done, that you are not aware off.
And while you are at it, also replace your fan-belt, as most probably it has been damaged by the off-centric revolutions of your pulley, over a period of time.
Another thing you have to ensure is that there are obstructions in the rotation of the pulley, which may have suddenly hit the pulley to damage it. Check your engine mounting bushes too, by reaching into the car and trying to rock the engine when it is cold. If it feels firm everything is AOK.
If it rocks then you need to change that too, 'coz at some point you may have peeled out, and the engine may have rocked, due to the torque, and in doing so, may have hit something which may look to be too far away, while the car is standing still.
also replacement of damaged engine mounting bushes would improve handling, by efficient transfer of power to the wheels.
See if this helps.