What will fit?

I'm looking into putting 22 inch rims on my 2006 chevy silverado 1500. I know that 22x9.5 with 305/40/r22 tires will fit i just dont know what offset to get. I looked at a +12mm offset but not sure if it will clear. Does anyone know the correct offset?

i drove down to discount tire when i bought rims for my last car. they were pretty helpful in finding the correct fit, even though i ended up buying my rims elsewhere.
i would imagine that any tire/wheel place that's heard the term 'good service' before will help you out if they can.
i did go back for the tires, though.