Are you lowered? How much? That will affect how the wheels sit in the fenderwells so my advice will best work on a bird lowered as much as mine (~2-3" in the front). They are 18x8.5 front and 19x10 rear. I run a 2" spacer in the front along with a 275/35-18 BFG KDWNT tire. The only time I rub is at full lock in reverse backing down a hill. A little specific, eh? I like that I don't rub at all driving but I think the wheels tuck a little too far in the fenderwells for my taste. Well, more truthfully they just tuck in farther than the rears because of how wide the rears are. I actually just ordered a pair of 2.25" adapters for the front to see how that looks. I think it'll balance out the rear better but I know for a fact I'll be messing with the plastic fender liner a bit. Not too much but enough.

For the rear I'm using an 4thgen LT1 rear axle so it's wider. I'm also using a 1" adapter along with rolled fenderlips. I think that's around ~2.75" wider than a factory thirdgen per side. From what I understand the rears are between 3.5-4" wider. If you're running a stock thirdgen rear I'd try a 2.5" adapter in the rear and a 2" in the front and be willing to pick up another pair of adapters if that doesn sit how you like it.