You should be running a 255/35 20 and a 285/35 20 for the wheel size your running and that is a hair on the big size tire wise. The wheel is in the range for the width but it is on big end Ideal for the rear would be 275/35 so if you wanted to you could take the fronts put them on the rear and sell the rears buy some fronts and you should be good. If you want drag radials on the rear then you'd need to buy those and try and get what you can for the current tires.