With the sectorsupport, the original nut seems to be replaced with one where the bearing is mounted on. I like to get this support kit as well for my box one day.
Yes, the nut is also the shaft that goes through the bearing, you do not use the nut that comes with the box. Before I put mine on the road I am going to trim it down some so it does not hang below the K-frame. In the following two pictures I added red dots on the nut below and above the bearing to help you see it.
