I'm not really sure as I don't have a 76 shop manual, do you? It's in there
But there've been changes between 72 and 74, and possibly from there to 76
The early "carbon can" cars had a vent can in the rear with the tank plumbed to it, and then a long vent line up front. THIS IS the vent for the tank and MUST NOT be plugged, unless you either install a vent similar to the 69/ earlier, or take other measures