So I've decided to do 2" body lift on my 99 based, I know I can do 30x9.5x15 or can I do 31x 10.5x15

 

30s If memory serves me right......if I remember correctly 3in body will let 31s fit.....I have a 6in sus on my 97 and was told 32 was max I could go with that

 

You could probably run 31's on factory rims depending on the tread, but you may rub a bit, especially with the suspension compressed. The most likely spots you would touch would be the back of the front fender-well, and possibly the frame at full lock if the tire has a heavy shoulder lug. A bit of trimming of the back of the fender will take care of that spot, and the frame rub (if you do) is very minor. Definitely not enough to bind. Mine did it for a bit when I ran 32's but it was only enough to shine the rust off a 1" triangle.