Hello Colin,
Irrespective of the new reg changes just thrown into the mix can I ask why choose side draughts rather than down draughts?
One of the biggest pains with the stock Alfa motor is getting access to the plugs and coil packs under the rear mounted plenum chamber. Switching to central ITB's eliminates this problem and gives great access to both banks of plugs/coils.
The forward mounted carbs/bodies would allow great access to the rear bank but severely limit access to the front bank instead.
Regards