You're in luck because this guy just posted this on my local forum.
20X9.5 +13
20X11 +6
He did not post his tire sizes, but with the amount of stretch going on out back I'd say he is running at minimum a 265, and most likely it is a 275/30 out back and I'd assume a 245 or 255/30 up front.
You need to be running 35 series side walls, you have 19s, a 40 series side wall will just be too tall.