It took a lot of time to finally get the axle squared up with the brake backing plate. I needed a VERY thin washer under the tab that secures the black axle tube to the brake backing plate (photo #1), but even a "thin" washer was too thick.
So I carefully ground down the washer on the Scotch Brite wheel to make it thinner. But that was still not enough.
So I used a block of wood and a heavy sledge to bend the tab in the direction that pushed it away from the backing plate. This gave more gap so that the thin washer finally gave the right shim space (photo #2 - see the thin washer under the black tab).
Then I put the axle in the wheel and screwed on the castle nut. I marked the axle (bolt threads) for the location of the cotter pin hole and drilled it on the drill press (photo #3).
The right brake back plate and axle attach bolt.
Close-up showing the thin washer under the black tab.
