We used the 21 gallon blazer fuel tank, we did not want to use the side filler neck either, so we took the filler neck from a 91 blazer and welded it into the bottom left (top) of the tank, filled in the old filler neck , mounted a in the tank fuel pump for TBI and then cut the hole in the floor to fill the tank. Here are the links and details:
start of process--drilling hole and getting ready to install new filler neck:
http://kieth.smugmug.com/Trucks/66-G...t3RHj&lb=1&s=A
after mods:
http://kieth.smugmug.com/Trucks/66-G...TFcBh&lb=1&s=A
installed in floor of bed:
http://kieth.smugmug.com/Trucks/66-G...0690&k=5cxcPkV
Look around in the build and you will see more details scattered throughout.
