Fitting kits are more for universal wheels (tsw,etc). You can get a different diameter ring to put in the wheel center to change the hub fitment, this is just a plastic ring which pushes in and can be changed.
Also some companies relate a fitting kit to - wheel bolts / nuts (ford use a dome shaped nut for alloys and flat for steel wheels), locking nuts / bolts
if thee wheels youre getting are the correct PCD and Offset then you wont need a fitting kit