With further research the transmission I'm describing (in post 34) seems to be a "Chevy/ GM/ Muncie 318 3-speed" rather than a Saginaw, which was just a guess. Apparently the barrel in the middle is referred to as a synchro clutch assembly and I believe it is a fairly unique design. It may not be the best one to get your teeth into if your learning about synchronisers.
But it's described somewhat in this video.
But it's described somewhat in this video.
