Most would just block off the return line. I would plumb it back to the tank as far as I could and "T" it back into the fuel line coming from the tank. This will circulate fuel through the lines and hopefully help with any future vapor lock problems. Use a line smaller then the main line for your return line.

If you pull the sender out of the tank, you may find there is room to add a line. A drill and good solder iron would be about all you need tool wise to make it work. The silver ( in color ) fuel line solders really good due to the coating on it. If you go this way, make the line into the tank long enough to reach 1/2 way down into the tank.

1937 Chevrolet Inline-powered Streetrod