With the top angle mount shaped and perfectly drilled, I then clamped the botton angle to it with all sides flush. Using a fine-tip sharpee, I drew the edges to grind down to make a mirror image part. I also match-drilled the 3/16" bolt holes.
I used my belt sander and sander wheel to make the angle edges, and my small 1" scotch-brite drill attachment to round out the center recess.
