so the front drum brake setup you posted a picture of is not self adjusting, but as I mentioned before the self adjusting hardware from any 60s chev / gmc half ton will swap on.
for instance here is a self adjusting hardware repair kit for a '66
https://www.rockauto.com/en/moreinfo...=1904&jsn=2967
Left and right are different, you need one of each for the front.
lots of pictures online how it goes together, just make sure you get things setup correctly for right and left