Slappy Mc Nasty
+1y
option #1. take the 2" or 3"fuel hose (that you do have, usually off the tank that connects the neck) to napa and match. just buy like 8" and 2 hose clamps. cut the filler neck in half and use the new hose/clamps to fill the gap.
option #2. get a lenth of steel tube that matches the diameter of the stock neck. cut the short neck in 2, weld in a new piece the same diameter you are short.
option #3. make a new neck out of the white pvc pipe along with 45/90 degree elbows, etc (home depot/lowes, etc) and use that as a template starting at the fuel tank opening and ending at the new filler caps home. now take that template to almost any muffler shop and they can bend out a pipe that will match from the tank opening to filler cap opening.