The suspension arms have been bolted to the diff casing. The bolt attaching the 3" narrow strip to the 3.5" standard strip is a shoulder bolt from a universal joint. It is passed through the 3.5" strip and then a thin washer is placed over the shank. This leaves a small undercut showing, which means the narrow strip can be placed over the bolt and then slid into the undercut, so that the 3.5" strip angles down a tiny bit more. You can also see the slipper shoes for the leaf spring suspension attached to the centre top hole of the 1.5" flat girder axle tubes. The spring is held vertically by the 0.5" bolt bolted into the slotted hole of the corner angle bracket.