So after searching the forums I still haven't found a 67-72 C20 with this setup, just a school bus and a '63. But looking at the second link there is a picture from someone with just two posts which shows me that I am likely missing some parts: I do not have a lever coming off the 4-speed tranny through the cab, for one thing.
All the past threads end the same way: what the heck is this thing and where can I find parts. Hoping someone on here might be familiar with this and can help me. Alternatively, I guess what I will eventually do is put in a regular old drum ebrake in place.
http://67-72chevytrucks.com/vboard/s...d.php?t=664961
http://67-72chevytrucks.com/vboard/s...d.php?t=622541