Hey I'm looking at some bfg all terrains. The size is 245 70 R17. These tires are about 30.5 inches and I was wondering if they would fit stock without any rubbing.

 

You'll be fine. That's close to the stock tire size, so you shouldn't have any issues. That tire size is actually closer to a 28.5 or a 29 anyway and a 9.5 in width.
30x9.50 is the largest size you can fit.

 

R17...? you have aftermarket or different rims? IF so, then really REALLY pay attention to back spacing. stock is 6". anything less, and your wheel will stick out more. awesome right? not so much, this will cause any possible rubbing issues to happen sooner as you turn the wheel. also, with wider tires AND less backspacing, you will be in for a lot of rubbing a lot sooner (potentially).

If that was a typo, be advised you should have 15" rims. there is some variations of this, but it's not likely you mistook 14" s-10 rims for 17's and if you sought out Xtreme rims, you'd know they are 16's