I have no idea what the vent is. Sounds strange to have a fuel vapor vent there. I doubt it would vent the crankcase since the valve cover has those. Either from an 80's slant nobody knows about or somebody's science project. My guess is the tube is a safety thing. The little hole you normally see is a drain (I think) for if the diaphragm fails, to indicate that and let you know (by smell) that gas is leaking into your crankcase. They might have decided that gas drips are unsafe. Anyway, you are ditching that fuel pump. Check rockauto, they should list all years that work. My slant has a block-off plate and an electric pump, but mainly because I plan EFI later.
