Well if you do the 150 kit it will give you a draw tube so that's not going to matter, if you do the AD II it will come with the kit to modify the sending unit. That gas sending unit will have the pump in the tank and the 2500 diesel will not.
I'm in the process of doing the same thing and i'm going to put the draw tube in then disconnect the in tank pump. The return goes back through the filler neck. You may have to measure though cause i think the diesel filler tube is larger than the gasser.