Before: After: (245/45/20, KMC Slides 651) "Cool Whip"

So I am ordering new rims. 20" (8.5") for my 05 chrysler 300 AWD. The offest is 38. I need help with the tire size. Do I go 255/45/20 or 245/45/20 or something else? Its my daily driver, please help guys!!

My name's Erik and I'm 22 years old and from Abbeville, LA... I own some websites which I run for a living, and am starting a job in Insurance Sales next month. My other car which I own besides the 300C is a 1999 Mustang GT (Chrome Yellow) with some modifications done to it (O/R X-pipe, SCT...