They do go on the outside. They just weren't designed for the backing plate for which the image appeared. As for inside/outside, I don't remember them that way but I changed to a 1969 rear end many years ago and so it could be the case. I remember them attaching to the backing plate with rivets or screws, nuts/bolts, something like that but on the same side (the outside). I looked in the shop manual but it showed nothing for that. I also looked through apx 2000 images I have kept (including around 60 on the braking system). No joy there, either. Sorry.
