My father was a truck mechanic,and in the school holidays we used to go out with the drivers.One truck was an International with twin sticks - they went over a big hill several times a day,and the little driver would duck down bellow the dash with his arm through the spokes with change both boxes at once.Great stuff.
In the '70's I was working as a truck mechanic and got to drive some twin sticks,mostly British trucks,but Internationals were common too.It was satisfying to get a good twin shift - up in one box,and down in the other.
The early Mitsubishi Mirage was a twin stick in some models - it was supposed to be a power or economy lever,but I used them as a twin stick.Working at a Mitsi dealer I still get to drive the odd old model - I can still twin shift with one hand....the apprentices go WTF????