Interestingly, the longer studs pictured might work for my bus, and here's why.. the 1965 original axle had a pullover rear drum, you could just remove it to service the brakes without getting into the hub if it wasn't leaking. I like that feature, but lost it when I updated to the newer T70 axle. Those hubs aren't pullover, the drum is behind the hub and you've got to remove the hub to even service the brakes. So what the new stud looks like to me, is it's made for the stud retained drum and that's why the knurled portion is out farther. The new bolt has a shoulder between the knurl and the head, which would locate the drum along with the hub pilot. The knurl would then go into the hub and hold everything tight.

1965 C60 school bus | 1967 GMC 6500 school bus