have addressed this several times green
i used 275/40's (michelin pilots) on my 97 GT rear wheels and used 275/40'(Dunlop Sp Sport 5000's) on my 99 GT
yes, it looked MUCH better from the rear and greatly improved dry performance but in really heavy rains and or light to heavy snows,...you loose traction due to the "plowing" nature of a wider tire. it does look really good in the rear. do not recommend them for the front however, it "pushes" the wheels and tires out too far for my taste