[CarlC]

The fuel gauge on these cars does not accurately represent the amount of fuel in the tank. The sensor is just a height gauge, but the tank has a lot more volume on the top 1/2 vs. the bottom. Once the gauge says 1/2, there's usually not much left, likely around 4-5 gallons.

You may want to remove the pump assembly from the tank to verify that it is still assembled correctly. Making modifications to the Spectre tank may have mixed results depending on the level of modifications, but adding baffles or in-tank boxes/check valves is not an easy task. Different pickup tubes, i.e. flop tubes, are not practical due to the shape of most tanks and usually don't adapt well without major tank modifications.