By axle stubs do you mean the bolts in the first picture? They're just steel M12 bolts that thread into the axle so they are removable. I am assuming billet will be a lot better for very low quantities. Depending on price I would make 2 sets, so four of each part, and if they're good I'll make 10ish.

They're kind of like these (you can see that it's two parts welded together).

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