Just a couple of suggestions. Backspace or offset needs to be dialed in just right with the wider wheels. Measure all 4 corners as left and right can be different. If at all possible, mount a sample wheel/tire to verify measurements.

Most 2 piece wheels can be ordered with custom backspace for little or no extra charge if needed. I wound up going with AR 17's on an E. 8" in front and 9" in the rear with custom backspace. Also 13" brakes up front. Done again I would use 18's as you are planning.