There's always turbulent flow in an engine, but I agree that a tapered cone transition piece would have to be fairly long to minimize disruption.
I might point out that:
a 2 X 1 manifold requires both carburetors operating simultaneously on a common plenum (2 X 1 separately is not possible due to the siamese center cylinder pair)
a 3 X 1 with a common plenum may run on the center alone (with possible distribution problems)
a 3 X 1 with independent runners requires all 3 operating
So there are operating differences as well as appearance.
How are your fabrication skills?
