I'm not an AD guy but here's the deal they are speaking of. The cab flexing they are speaking of is the cab flexing relative to the frame. If you had hard line from the tank and attached to the frame and to the engine it would theoretically stress and break because the cab "moves" independent of the frame because there are rubber pads, a small cab to frame mounting area, and allowable twisting in all the chassis. I don't know if the tank is attached to the cab, if it is, there is NO flexing between them to worry about. So you can put a piece of standard rubber fuel hose between two sections of fuel line tubing BETWEEN a point where the tubing is attached to tank/cab and attached to the frame, as in: clamped to cab and frame. (does not have to be a long piece). If the hose they show does that, it's good to go or if you want to be totally stock. Don't let that special hose bother you if you don't want to buy it. I still have the same question you have that no one has answered for sure and clearly. Do you hook the line to the drain hole or do you get a sender with pickup? Once you get that answer, you simply buy fittings that fit the threads you have all along the system/line you have with an appropriate short section of fuel hose you get from O'reilly's, or other. I plumb with fuel line sections I get from them and bend to suit. When I need a rubber section I just scoot the nut back, slip on the hose over the flare and clamp it with a hose clamp, then clamp the other end of hose to the next section of the pre-flared, store bought, tubing. Piece of cake. Buy a bunch of lengths and take back what you don't use. You need to tell these AD experts what year and model you have. Sounds like there may be differences in early and late AD line hookup.
