Best size tire for 2001 GMC Sierra?

[coylittle1290]

My friend has a 2001 Sierra. He has 255/70/R16 on the truck now. He likes the rims he has but wants bigger tires. What is the best size for him to get. We don't really understand what the numbers mean. Thanks for all the help. I think he wants the truck to sit an inch or two higher. Thanks for all the help. He also is thinking about getting all terrains, any recommendations? Also how much is he looking at spending? Thanks a lot.