This task was done at the "Detail Day" event.
Go to
http://geocities.com/provamo72/ Select Past events, then Detail Day for images.
There is a short fuel-grade rubber hose from the filler to the elbow that is connected to the tank. (On most cars with the outside filler.)
Looking at the image, you can see access is from below. Take the wheel off, splash shield if you have one, and reach up with a screwdriver, to loosen the outside hose clamp.
Loosen the other hose clamp, at the elbow on the tank end, from the engine bay side.
Take off the panel that covers the top of the gas tank, and for easy access, take out the 1/4 window (with frame, gasket and all).
Remove the 4 bolts that affix the outside filler "neck". Twist and pull. If tight, squirt some WD40 or ? between the hose and pipe. This gives you some flex room.
Fuel grade hose can be found at most auto parts stores, you need 6-8 inches. It's a (expensive)firm, thick, tough-to-cut type of hose.
We put one side on, (tank), then the other end took a little persuading. Finally stuff the filler neck (the outside ring)on, and bolt back down.
If nuts, washers, or bolts fall off...
Most will land on top of the tank, some might hit the ground.
Don't let one fall between the gas tank and the body, as it could get 'lost'.
Chuck Melton