Reverse side of axle bearing block mounted to 3" x 1" U-channel. Slot in the frame rail allows for adjustable height of wheel with the rotation/replacement of the bearing block without having to manufacture a new frame rail. Bearing block is held in with four bolts (threaded holes in block = no nuts needed). “Dead” axle is kept from pulling out with an E-clip.
This view also provides a closer view of a riveted frame joint, which was first shown and discussed in this thread here.