72 340 pass side manifold
in my mind, a center dump 1-7/8" manifold should flow equally the same as a rear dump 1-7/8" manifold - can't imagine a reason why a rear dump would 'flow' better, but even if it does it can't be a lot better, but either way I've decided to go with the 340 manifolds and call it 'good enough', probably more than good enough.