I ran a BB and 245/75r16 KM1's on stock rims with no spacers for years. It would only rub in the front at full lock.
If you want to run a narrower 33" tire, you can get by with 4" and minor trimming. If you want to run a 33/12.5, you will have to do some considerable trimming unless you limit your uptravel. I believe that Iceland style fenders remove quite a bit more material from the top of the wheel well, so that would be a better bet to keep a LCOG.
Here's my rig on worn out 33" TSL's at 4"
Here it is at 6" (BB + 4" IRO LA's)