Yes so this is what I think is the issue I have a 574s (actually two when I go dual carbs)
574s pic notice where the throttle will connect to
574s at 5 o'clock
684s at 3 o'clock
I think this is the one that must have been on the motor originally 684s
684s pic Mike said unfortunately W-1 could have anything on them as they get swapped around a lot.
Looking on ebay I notice a few of the carbs have the throttle connector bent like one of mine - so I will just make a rod with heim joints. Will be a bit more secure (than a hole and cotter pin) and still "Made in the USA"