Guck mal hier:
The filler neck is cut off by cutting a circle around it, leaving a circle of
tank material in place around the neck. Then this position is blanked off by
a round plate welded in place. A new circle is cut out in the new position and
the neck is welded on there. A notch is cut out of the tank front area and
a patch welded in, as seen in the photo.
Welding on gasoline (petrol) tanks is VERY DEADLY dangerous and should be
left to professionals