On my 52 Flattie, I noticed (um, how could you miss it...) the road draft tube. What exact purpose does it serve and is it really a necessity when rebuilding. The reason I ask is that I have an earlier Edelbrock performance manifold without said tube and would like to use it, if possible. However, I don't have any qualms about getting a correct year manifold with the road draft tube casting if it's really needed. Can anyone shed some light on this one? Thanks!