Hub vs flange mounted brake drum

[rreegg]

Making the rounds looking at brake drums for '88 F250 w/ 3" shoes. I'm curious if anyone knows what the difference is between hub mounted and flange mounted brake drums? Looks like the flange mounted has a rectangular tab on the exterior but not sure what that's for, it kind of looks like a long wheel weight.

I have a hunch they're interchangeable but cannot find much anywhere explaining the differences - doesn't the drum just fit onto the lug studs?

 

[u2slow]

Sound like "backmounted" vs slide-off drums.

On older full-floaters, drums were nearly always backmounted. You had to punch the studs out to take drums off the hubs. In the mid-80's Ford changed that and the drums slide off; dont need to remove hubs.

Drums and hubs are cast to fit one way or the other - not interchangable.