Vapor Lock question

First off, nice car. Secondly, long story short, being a 72, u definitely had some sort of charcoal canister originally, which means u have more than just a fuel line coming out of the tank. I would follow those other lines, most likely someone deleted the canister and figured they should just plug the lines. U need to leave at least one open as a vent. If u drive 3 miles, shut the car off and open the cap and release a vacuum than u have very little if any venting at all.