I started on this mod yesterday on my 99, and my Internals must be different or you the write-up left out a few things....
It had pieces attached from the Inside, plus on my driverside theres a "skid plate" type box attached to the frame rail and the Inner quarter panel...I got fed up, said F It and Just cut the whole thing out, no bending or anything, so now Its cut straight across, then I grinded the metal down smooth. Now I Just have to find a way to patch the openings on the bottoms with some sheet metal so crap dont get in there.