Re diff cover
Good idea. I just took a look (that rhymes?!?!?!)

I'm a piano technician, and I can make that with metal cutting blade on my bandsaw and Northern Hydraulics welding rods. Flat plate (double thickness at edges) Round tube cut for ring gear and spacer. and tapered round tube down to plate. Bobble strut bracket welded where you want.
After reading this discussion, I realize that I can make the spacer with no machine shop. I have set of center punches for dead center location of holes. Small lead drill and then final drill size. (Drill press has compressed air cooling)
All I need a machine shop for is sufacing both sides of ring spacer and check balance????
1/4" plate for cover good???