A 1996 XJ doesn't have a return fuel line.
The plastic line you're seeing must be a
vapor return line from the fuel tank.
Since there's very low vapor pressure involved,
you can use just about anything you wish; metal,
rubber, plastic, etc.
There's a metal line called NICop that's a blend of
nickle and copper that is easy to bend. Or you can
just pick up a roll of plastic line...