I am looking at buying a local set of R58 cobra R wheels with BF Goodrich g-force rivals in 255/40/17. I was wondering if these would fit my Foxbody with IRS. It also has the front disk brake converted as well to 03 cobra brakes. I dont think that clearence in the front should be a problem but I am worried about the rear end. From what I've found out backspacing is very important with the IRS set up, any help or suggestions would be appreciated. Also appologizing in advanced if this has already been asked.