The Task Force trucks have the steel line exiting from the top of the tank, going to the right and behind the tank through a small hole in the floor, then over to the right frame rail and on to the pump, I have no rubber or other flex connection in the line until it gets to the pump. The flaring tool you show should serve you well for auto, propane, and any other soft tubing flare jobs.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy