1988 Lincoln Town Car The return gas line leaks.

The return line is metal along the bottom of the vehicle and rubber from that line to the engine so the engine can rock back and forth. You can use rubber to replace a steel line but only if it won't be near the exhaust system or where any damage could occur to it. It has to be fuel hose though. You can buy vacuum hose the same diameter but that will usually not be gas-resistant. Any rubber fuel hose will work for the return line because there's no pressure there, but the supply hose will have around 15 pounds of pressure if the engine uses throttle body injectors. Standard fuel hose used with carburetors will hold up to that. Carburetors handled from 3 - 5 pounds. If you have an injector for each cylinder, those systems can run over 50 pounds of pressure and you must use "fuel injection" hose. I also strongly recommend using fuel injection hose clamps. Instead of the "aircraft" style that uses a worm gear to tighten, fuel injection clamps are a nice smooth band that is tightened with a long thin bolt and nut. Every auto parts store will have them in a few different sizes. Most fuel return lines use the smallest size, and most supply lines use the next larger size. Those don't cut into the rubber when you tighten them.