Another thing is, you are right, no pump in the fuel tank, just a gauge and filter. The gas line is angled down towards the fuel pump. If you disconnect the rubber hose that jumps from the sub-frame to the pump, gas will drain out of the tank. This way with the car level on the ground, gravity will feed gas to the pump. The pump feeds gas to the carburetor. I'm not sure what year this started, but on most AC equipped cars, there is a third fuel line that recirculates the extra gas back to the gas tank. This is to keep fresh cool fuel at the carb and help prevent vapor lock. Otherwise there is just a supply line and a carb line.