Depending on the wheel and tire choices, spacers are often required. They can be obtained from H&R or Bloxsport on eBay. I have 35" tires on my SWB W460 and they will lightly rub the radius arms at full lock; it is necessary to trim the frame tubes behind the front wheels. Depending on your setup, large tires can also rub the outer corners of the front fender flares. The rears tend to rub the body seams at full compression.
I should point out that the rubbing is harmless and other than making a little noise occasionally, the benefits of large tires far outweigh the trivial nuisance. My two cents.
"The way you think is the way you live"