Fuel tank venting
If you have the skill I would duplicate the non evap AKA 70/ earlier setup. Braze or otherwise install a fitting up high in the filler tube, bring it up high in an upside down "U" near the top of the fender and back down the tube through the trunk floor gasket
The original vent was the 1/4" tube going clear up into the engine bay and connecting into the "carbon can" evap control system