2536771 CAP 4BBL Intake Manifold Port Plug ?

Dana67Dart said
Logical, but why make two castings one with a port and one without, i mean mine has no way to get to the runners and the casting looks like they had a swappable mold from the bottom side.
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No Idea. They did some strange things with California cars. The carbs didn't have vacuum ports for power brakes back then I don't believe.