For the fox body application, we recommend a 255/40/17 for the front, and a 275/40/17 for the rear. A 315/35/17 would work as well and give a thicker appearance, but will require massaging the inner wells and fender lip for proper fitment depending on how low your car is. We do not recommend going larger than a 40 series.
I am not aware of anyone making a 315/40. They are only produced in a 315/35. If the car is extremely lowered then yes, you will need to roll the fender lips as well on the rear. Fronts should be fine.