06 Silverado 1500 - What Is The Correct Offset

[jdub4420]

I am looking to purchase a new set of wheels and tires. I have heard several opinions on what is the correct offset for the wheel. I am purchasing Ultra Mammoth 20" wheels, reccomended 0 offset, and Toyo 305/50r20 A/T tires. The reason I ask is that several people have said that a 0 offset will be just fine with a little trimming inside the front wheel wells with about 1/2 inch of rubber outside the fender. While others insist I must get a rim with a 15+ to 20+ offset... any help? Also will a leveling kit help with the trimming as well.