285/75-16 and 305/70-16 are both considered 33s. The 285s are just under 33" and the 305s are just over 33". The 305s take more cutting and usually the actual fenders.
Some pounding (the inner fenders and pinch weld at the back of the front fenders) is needed to run 33s.
Also when stuffing to the bumpstops, they will rub the tops of the fenders. A 1" or more body lift is usually added to eliminate that rubbing.
On stock wheels, some 33s rub the upper control arms at the ball joint. This is actually worse with more lift due to the ball joint rolling out into the tire. With this said, they may not rub at ride height but may rub at full droop. Wheel spacers will eliminate this.
Wheel spacers will increase the fender rubbing on the front tires. Spacers increase the arc that the wheels make when turning.
Sometimes 33s will rub the washer bottle.
Different makes and models of tires run different actual measurements and some will rub more than others. Some have bigger lugs on the sidewalls that will cause more rubbing on the UCAs.