For a fuel return line, first look carefully at how your lines are connected.
Maybe take a picture, even.

Next go to a junkyard,and find a car WITH return line, (not even
the same/exact year)and remove it; INCLUDING the extra piping, solid and flexible, back at the gas tank, that allows gas to return into the tank. This will show you the route that you will follow for your return line.

If you have to cut a line, you can enclose the
cut *inside* a rubber hose. That is how I would plumb a return line.-Bob