5.0sicness

I'm looking for a new set of wheels and tires for 1989 GT hatch back. The car is pretty much stock but still loosing a lot of traction off the line I just got drag launch 50/50 rear shocks with air bag, 70/30 front struts and eibach 1.5" lowering springs. I want the widest tire I can get with out having to move or cut a bunch of stuff, how wide of wheel and tire can I go before major modification? Also all I can find for my car is the cobra r wheels with out going to a five lug conversion does anyone know any other cars that have the same lug pattern and off set as these fox body mustangs? Thank you for any help.