The 38mm Webers are pretty tame when you consider that guys use twin 45 DCOE's on 2 litre engines (I still don't know why anyone would want to use them on a road car...) . The 32/36 Webers aren't that far from spec when compared to the Mikuni's used on 2.6 Astrons (same size throttle butterflies). My opinion? Use the 32/36 Webers. They are automatically bigger than the Mikuni/Solex carbies on your twin carb rack. Bear in mind the twin carb set up isn't for full on top end power - it's for beefing up mid range without killing bottom end and response (I think the 38mm synchonised downdrafts will be overkill and would wreck performance). Once you have a tune that works with the twin carbies, you'll find there's sweet spots in the acceleration/rpm range where the engine will want to pull like a train. Also, have you considered an adjustable cam gear? It might help with getting the cam into a power band that is optimal for the carbies.