69 Chevelle Wheels and Tires

[Redsplitwindow]

I will be lowering my 69 convertible Chevelle in the next month or so.
12 Bolt,4 wheel wilwood disc brakes.
I want to run 20s in the rear and 18s on the front and would like the center of the wheel lip to cover most of the sidewall.
Suggestions on Rim widths ,back spacing and tire size would be greatly appreciated.
some photos would also be cool.
I will not be rolling my fender lips.
Thanks
Dave