SC pulley mods

[ArcFlash2]

I have a 2001 GTP, bone stock. I'm looking to throw on a smaller pulley just as a cheap way of getting more power out of it. What do you think is the smallest safe size of pulley possible without having to add supporting mods? Is it even possible to add a pulley without other mods? (ZZP pcm, downpipe, intercooler, CAI, etc)