I have 17" GT5/5S spec wheels 10" Fr & 13" Rr, if PIM supply narrower wheels that have the correct offset then it is purely a matter of taste as the width is all coming off the inside edge. I'd want to see a set on a wide body to assess where they actually sit to the fender lip. Wide body cars look stupid if the wheel is set very far under the flare IMO. I looked at the PI website and personally wasn't overly taken with them,yes they have 10 spokes but they are a flat center no dish like a real campi.
An 11 inch rear will still take a 335 profile tire, the 8" front you may just get away with a 255 profile, but 235 is recommended, whereas stock was 285/40. The narrower rubber up front will help reduce tram lining and ease parking lot steering wheel effort. What do you have on the Group 4 as it is now and how do you like the drive?
Whatever you do I would suggest (if not already done) to modify the upper a-arms to provide additional caster, a wide body really benefits from it, I have 7 degrees.