Spacer for Z06's on 99 Z?

I hear i have to have a 58mm spacer for the rear wheels of OEM Z06's to make them fit. my question is, where the heck do i get the spacers, and do i need them on the front for the 17's? Also, will the car look good with 18s in back and 17s up front?

TTT, i want to know this too, i know you dont need spacers in the front, but i dont know about the back and my rear ones are the same offset.
thanks if anyone can help