Here is a view of the gas tank door. The “scratch protector” shown was an add-on, but is quite common for this model of Chevy. The scratch protector is held in place by 2 flat-head screws at the bottom of the opening.
The neck of the tank is supported by a metal strap (left) that is held in place by a sheet-metal screw. There is a sheet-metal pipe surrounding the neck, shown on the right as seen from under the car, looking up.
Fuel Tank is supported by two straps which are held in place by two bolts at the front and rear. There is a drain plug near the center of the tank. Apparently, when I parked the car --15 years ago-- I didn’t bother to drain the gas tank. There was about 5 gallons of gas left in the tank, which had to be drained. The old gas smelled horrible! It took days to get the vapors out of my garage.