Lifted Truck Pulling a Fiver or Gooseneck

Not a good idea IMO. You're raising your center of gravity which will tend to make the truck less stable, and when towing less stable is not a good thing. Like was mentioned the new trucks are already too tall(IMO) and cause clearance issues even without a lift. You definitely will have trouble finding a 5th wheel/toyhauler that you will be able to fit under.

I think you'd be better off foregoing the lift if you plan on towing anything of any size. JMO of course.