Moog is junk now. I've gotten lower ball joints that were ridiculously tight, ones that had slop straight out of the box, and even one that came with a castle nut that had no threads in it.
Proforged has been the best quality OE replacement parts I've seen lately. The other option is to spend a bunch more money and get race stuff like Howe. But Moog is hot garbage.
Are you sure? I'm not. I've seen drum brakes on A bodies as late as 1976. Maybe they modified the 73-76 Drum knuckles to match the mounting points of the disc units?
The upgraded 10" drum knuckles that started around November of the '73 production used the same lower ball joints as the disks. Not sure what happened from August to November with the drums but I don't see a reason to restart that discussion because the parts references used by most places won't deal with it anyway. If you look up a '74 Dart or Duster it only shows one style of lower ball joint (the later disk style) and does not specify disk or drum.