I run 17s on the front and 18s on the rear of my Super Bee, and my personal opinion is that our old Mopars need to be lowered a bit to look best with 17 or 18 inch wheels and tires. I dropped mine approximately 2".

Also, make sure that you run a tall enough tire on the rear to fill up the wheel well. There are actually not that many 18 inch tires that are both wide AND tall enough to fill those huge wheel wells.