Chevy 4x4 Help !!

I have a 2005 Chevy Silverado 2500HD extended cab - I want to put some new tires and rims on - can anyone help me - I need to know what the largest size wheel / tire combo is that I can order w/o having to lift at all
Thanks

go to a rims place and tell them that you want new rims and you want the biggest you can get. and y is this in the light truck part?