Pulley for GTP question?

I was wondering.. if I was to put a 3.4" pulley into my GTP, would I need any prior engine modification? and how much would it cost? is it around 70 for everything, what about installation? I've focused on the appearance of my GTP mostly, and now I'm wondering why? I'm going to start putting money into my GTP and with the lack of money I have at the moment, I want the cheapest way to upgrade my supercharger.. thank you

If you don't get the exhaust first you will probably have some kr (knock retard) You also have to get the tool to emove the pulley. my brother did his by having a person from washington grand prix club use his tool. The tool costs 150 I think. My brother also did his pulley before exhaust, and it seemed to run alright. I'd just be afraid of too much kr. It's a pretty safe mod though, and the difference is huge.