Mark, you are very right that normally the "velocity stack" (= carb air intake) does not have to be removed. Only when taking the carbs completely apart.
In my case, the "new" carburettors came without them, so I will have to use the ones from the old carbs. I don't expect problems fitting them again as long as all the screws holding the carbs together are placed but not tightened. Tightening them is the last stage of assembly.
I will go through the manuals to see if there is anything more specific that needs attention.
All the best, Rob