I don't seem to have the "tower" you were talking about (I was wondering about those two holes...) but I do have this:
Looks like it's a cable tensioner? Doesn't it? And nope, I don't have that part... ugh.
Today, I also got a cable and sleeving for it. It's a bike cable cut to about 6 ft in length, and the shop gave me sleeving to go with it. I'm sure threading it through is gonna be a blast... I also got some gear oil as when I replace the shaft I have to drain the oil...
Nevermind, just realized the piece in the picture is just supposed to be for the lever end of the cable. So anyone have an idea where I can get the piece to put on the gearbox?