Brake Drums
Besides bolt pattern and shoe width, verify the hub diameter (center hole). I know hubs (and bearings) were smaller in slant six cars (all?).
In the late 80's, I went to 4 junkyards and couldn't find the smaller hub for my 69 Dart after it spun a bearing, which is a common problem. Not sure why Chrysler had to make them different. I even had factory air so weight was almost the same.
Centric has the best details. They have drawings with all dimensions. Look on
www.rockauto.com or find their on-line catalog.