You would but then what do you do for side plates, and center section. Sometimes it's nice to take the time to buy the material and build a notch yourself. But on the NBS the frame has a contour just in front of the axle which might throw some people a curve ball.
If you want to do it yourself it wount hurt my feelings. I was just trying to offer you a notch that's already designed and made for your truck that could save you time and effort.
Good luck with the project which ever road you take. just make sure it's on the correct side of the road, and the wheels are down.