Raw fuel smell with slider open

[B_derK20]

Hi all. My '83 K20 makes me sick every time I drive it with the rear slider opened. I looked at the sending units on both tanks and there are 3 lines for each one. The large ones go to the tank selector valves I'm guessing and Im not sure what the other ones are for. The 3rd line on each sending unit has 4 inches of hose with what looks like an axle vent stuck into it. I'm guessing that's where the raw fuel smell comes from. My question is is this how GM built it? The truck was built in Canada and I can't see where it ever had one of those charcoal canisters by the radiator. Would putting one of those in and running the vent lines from each tank to it fix my problem? It's hot here and I really need that window open since I don't have ac.

Thanks!
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