The air boxes are all the same. The disc that sits behind the filter screen (away from the engine) has the holes. Three for the smaller carbs and jets, six for the larger.
The smaller carb has a 10MM throat, the large is 12MM.
How to spot them in a glance:
On a 10MM, with the choke blade in the open position, there will be a space between the edge of the blade and the edge of the throat.
On the 12MM, the edge of the blade is almost touching the edge of the hole.
Hop up tip that probably doesn't work:
On my Grande I noticed that the outside end of the throat had a sharp edge on it. I sanded it round with some emery cloth, them polished it with white rubbing compound. A poor man's velocity stack! If you try this, don't reshape the throat. just round off the sharp edge.
I think this is the equivalent of disconnecting the governor on mine.