my buddy has a 2001 1500 4x4 sport with a 5.9 and he put 305/70/16 super swamper tsl radials and they fit fine.. pretty sure thats a 33"..

 

285/75/16 is what I'm running on my truck and when I bought it a month ago, I had to get new tires put on it and I asked the guy what my tires were in inche's becauseI've never looked into tire sizes before but he said that 285's are 33". I wanted 35's but he said that unless I'd put a lift kit on my truck then he wouldn't suggest going higher then 33's because the 35's would rub on turns and what not.

 

Congrats on the truck.