350 is for the manifold [ i know its steep ]
from what ive read on club gti 45s are better for valvers 40s are considered too small, with bike carbs the suzuki gsxr750 or early gsxr1000 carbs are good the earlier carbs can be unbolted from each other and spaced out to match the manifold. 42mm bike carbs are supposed to be the minimum size to use have a read of the carb and throttle body section on cgti, it gives lots of info on the pros and cons of most set ups