While my Truck is a Task Force and not an AD, this still may be of help. On the Task Force there is a fixed solid line for the tank that at transitions the a flexible rubber line to the frame and back to a fixed solid line to the fuel pump. At the fuel pump it uses a flexible rubber line
All of that said, I used a flexible rubber line from Jim Carter at both locations. I went with this hose solely because at had threaded fittings.
https://oldchevytrucks.com/me607.html
