Its easy to do as long as you can get your fuel lines off, if the dorman fitting is angled wrong its a real pita... don't ask how I know. I ended up (on my Dad's truck) dropping the driveshaft to make more room, lowering the tank a bit and then pulling all the fuel lines out of the holders on the frame. That way I could lower the tank without unhooking the fuel lines. I wish I would have done that before I sent three hours with my arm jammed up under the truck trying to get the fittings loose... .
end of story the mod works great and Dad can fill his tank full and much faster.