If I were you I would get a small flashlight and take a peek into the tank and look for serious corrosion. Also I would remove the petcock to see if the filter screen is still there. If you shake the tank and you can hear stuff rattling around then you don't want to use it without cleaning it. That junk will get sucked right into your carbs.
Just turn your petcock to off, disconnect the fuel lines and remove the tank.