On old willys, the wheel hubs and brake drum are "one piece" because the wheel studs are swagged or cold riveted. The wheel hub is mounted outside, so you have the wheel hub, brake drum and wheel studs. In new modern willys, the brake drum is not "attach to the wheel hubs and they are not mounted in the same way. You have the brake drum, wheel hub and wheel stud. The brake drum is maintain in position by three screws but you don't really need it.
I tryed to attach pictures to show the difference between a brake drum mounted inside and outside.
I found this word document that explain how the stud are swagged.
Please feel free to add yours comments to explain it better than me.
