Looking for new wheels

[My 91]

Hi, I have few questions that I'm hoping someone out there can help me with. I have a 91 white coupe that I have been wanting to replace the wheels on for some time now. My first preference would be a set of C5 Z06 gun-metal gray wheels. I would consider polished aluminum but I don't want chrome. I thought the darker wheel might look better on a light color car. Does anyone have a picture of a white C4 with gun-metal gray wheels on it that I can see? My next question is the size. Right now I have all 17 wheels. I see sellers on the internet sell 17" for the front and 18" for the rear. Are the 18" rims much wider and will they stick out past the fender wells? Will the offset make a difference? What size tires would you suggest if I have 17" up front and 18" on the rear? Thanks for your help. Wayne