My '41 1/2 ton has a '54 235. On the intake manifold just below the carb there is old "line" that has been closed up with a screwed in brass plug. Looking at pictures of other similar engines, I'm not seeing the same thing. However, when looking at '41 - '46 engines, I see this line running somewhere toward the back part of the block. Is it possible that a PO put an older manifold on a '54 block? What is going on - and more importantly what should I do?