The stock 19" Rims run a +41mm offset
If you're staying stock height you "might" be able to squeeze a +41mm in that wheel well, but you'll have to stay to the x8 or x7.5 (ie. 20x8 or 20x7.5) anything wider (ie. 20x8.5 or 20x9+) and you'll rub or it just wont fit.
Your best bet is to talk to a rim/tire shop, see what they recommend, they can measure and use test wheels to find out.