he'll be fine, my friend runs a '97 cobra rear with some 94-95 17" tri-bar's and its all bolt on and perfect. i also have the M2300K kit on my car and run 17x8 bullitt's identical to the 01-04 stockers, just in black, and the rear track is slightly wider than stock and looks WICKED
I agree, the wider rear looks great with some wheels, I love the wheel right at the fender lip. But there will be wheels you cannot run because they will stick out. I researched this for months before I bought parts, and decided on the narrowest set up, to run some 10" wide rear wheels. I am not sure what wheels dont work, but running a wide rear set up, might limit you!