Question about gm factory 20" wheels

I think it's time to upgrade my old eagle alloy 17 in wheels. Gm has several good looking 20" wheels out now. I have a 4/6 drop on my Chevy and I was wondering if any of you are running a factory 20" and if so is the offset/backspace dimensions working out? What size tire are you running on those rims?

Pics also if you got some.

Thanks for the help

From what I have seen on the single cabs everyone usually runs a 275/45 tire and the factory offset works just fine. Google it and you will find an endless supply of pictures.