the sending unit you have is for an early pinto , single outlet , after market part number FG178A , the One you need is FG178B it has two outlets , the extra tube is a return from the fuel pump , it suppose to prervent vapor lock in hot weather , so if you live in a cool area and does not get over a 100 degrees you just could plug the small pipe one the fuel pump or just change to a fuel pump that does not have it , hope this helps you