40's may have came with 32's, but I don't know if they are interchangeable.
Why do you think you need smaller vents? I had those carbs on an otherwise bone stock (right down to the muffler) 1600 and they ran great...
i miss a bit off bottomend performance... could be corrected with jets, but the engine really comes to live over 3000 rpms and the engine was build for a maximum off 5500 - 6000 rpms due to the cam and type3 cooling. so all the power i can get in lower rpms would be welcome. just trying to make what's good, better
on Bergs site they say that 40's and 42's use the same vents