Had the same questions you when I made the move to a TC.
I overcame the rails left in the bed by placing the "Pink" foam insulation on the bed by cutting in 3 pieces and fitting 1 piece forward of the first rail, 1 piece between the rail, and one on the rear.. Glued the pieces to 1/4 plywood to the bottom to add some durability and increase the clearance to make sure it the rails would no come in contact with the TC bottom.
The dealer put Airbags on for me as part of the deal... I later added an onboard compressor to allow me to adjust the pressure while on the move.
Recently added a metal spacer on the overload spring to allow improve the stability with and allowed me to reduce the air pressure to the airbags.
My truck is a 2005 and it handles the Lance 981 Max with no problem... Feel the airbags and spacer were a good choice... In addition, I added a rear view camera which paid for itself many times. Without it there is a blind spot that can't be overcome by mirrors....
I have 1/2 inch clearance between the TC and wheel wells... close fit and had to practice a lot to get it on and off the truck....
Good Luck and Happy Travels.
