I would like to know what parts are needed for the "complete" cowl induction hood. I know of the air filter housing, the seal, the steel ring and flapper (I've seen this all in the Ground-Up Catalog) - but where I'm confused is in the vacuum controls. I know there is a vacuum control that operates the flapper, but I understand there is another control that lets air into the top of the filter/carb setup? I have a '72 SS 402 with regular cowl hood and would like to build up a complete induction hood to have as a spare (nothing comes off this chevelle that I don't keep!). I've been told that the '72 SS was not available with a cowl induction hood, yet another source says Chevy only played it down in advertisement literature. Help appreciated.