yeah the triple side draft webers have been done in australia on the 2v head, you need a special intake manifold obviously but i've seen them around so someone is producing them.
the triple weber setup is hallowed here in aus, check out anything on the hemi six found in the valiant chargers and you'll see why.
the webers are notoriously hard to tune apparently, but i guess once you get them set i hear they stay in tune well. the real attraction with these carbs imo is that they'll give you the maximum na horsepower for these engines.