There is a small flex line coming out of the gas tank that connects to the hard line correct? About a 4 inch hard tube coming out of the tank, a brass fitting that allows for a petcock on one side, rubber tubing about 6 inches long, then the hard line to the fuel pump. Right? All AD's were stock that way.
Thats the only flex line which makes sense, since the cab moves sufficiently to warrant it.
1954/55 A-D's were plumbed differently, with no petcock (the fuel exited the tank at the top of the tank), but they still had a short length of flex line between tank and fuel pump.