There are chokes that are mounted vertical to the carb and operated by an up/down lever on the far left carb and there are chokes that are mounted horizontal to the carb body that are activated by sliding left to right, either by a cable actuated at the left handlebar switch OR by a pull/push knob located on the farthest left carb. Your carbs have the horizontal chokes that are linked by that long rod. On that rod there are detentes for each carb to affix a screw held clamp so they all work in unison when activated. Seems you are missing a clamp or two. Whether the three chokes are actuated by a single knob affixed to the end of that rod at the left carb or by a cable remains to be seen.....probably a knob.
Looking at the second pic, far left carb, you can see the detente. The clamp and holding screw just need to be moved so the end of the clamps mounting screw goes into that detente. Can't see the middle carbs choke clamp. You might have all you need there to put these right save for the knob.
