[Alan Roehrich]

Very common on older vehicles. It was intended to inspire people to pack the bearings every time they did a brake job. The other thing it does is makes sure the drum stays located the same way on the hub. So once it is balanced, it stays balanced. And when you turn it on a brake lathe, it is turned concentric to the hub.

Those old drum brakes aren't great. You can make them better with modern shoes and drums. But you can't make them disc brakes. However, GM was good enough to keep things very interchangeable, so later disc brake stuff swaps right on. On my 70 C-30, I swapped to 80 C-38 A-arms, spindles, rotors and brakes without changing anything else except the master cylinder and the proportioning valve. Now it is a K-30 4X4, but that's another story. If your truck is six lug, and many were, there were a couple of years they made 6 lug disc brakes on the later models. If it is 5 lug, then the stuff off of a 73-87 C-10 will swap on.