i got an 06 2500hd, green keys on the way....

is there really a difference between the tires ???
305/70 R16 or 33x12.50 r16

what would fit better ?

same size as far as i know.

same size..the 33 might be just a bit wider than the 305, but that is it. I would not recommend these for the stock rims. Way too wide. It can be done, but I would not do it. They will look better on a wider rim too.

damn close any ways, seems that the 305 is a little smaller but only 1/2 inch and a touch narower

beat me to it BOBO !

305s are a truck size(Load D) Usually the other ones come ina D load too but the poundage they can hold is low. They generally have a higher load rating. If your going to put that size on stock rims be prepared to get crappy milage out of the tire, crappy handling, and a crappy ride out of those green keys without extended shocks.

If I were you I would get a 285 (Max size for stock rims), or a 285 on an 8" rim. They will look better and wear better, and you wont have to chop the heck out of your new truck. If you do decide to do 305s on aftermarket wheels they will rub... bad.

Trust me man, Ive done this all step by step. From 245s to 265 to 285s on stock wheels with no torsion bar crank. Then Cranked T-Bars, to Green Keys and Shocks.

Now I have Green Keys with the full Cognito Leveling kit with the Braces, and Sleeved my tie rods. For the Wheels and Tires I have a 285/70.17 on 17x9 wheels. They still Rub a little bit but not very bad. They are narrower than the 305s

Kinda depends on brand if the 305 is a true 33 or not. Some brands a 33 is only 32.3, sometimes it's 33. Same with the metric sizes. Some are right up there and some are a little small. Hard to tell without measuring it mounted on a wheel.