Little to none as far as I know.

 

Well that's quite interesting. I figured the frames would have been different.

 

I also have a 1500 with a 5.9 and and 9.25 rear and everything and I haul a 4500 lb trailer occationally. When my work truck breaks down. And I know when I put the trailer in our 2500hd work truck it kinda levels the truck out. It bearly moves. But when I put that trailer on my 1500 it goes way down and it makes the front end float alot on the highway. And I get extremely worried about the 5lug on the half ton. Idk if I should worry about it. But I just can't see it holding up for a long time. They make springer helpers u can order that bolt on to your set up. It goes above the current springs then has bend braces that attaches to your springs. I don't think u have to take anything apart on your truck just bolt on. If u can add some spring helpers, maby change to 8 lugs, and equip your truck with electric brake controller and put electric brakes on your trailer. I think u could definitely manage to haul the trailer your consideraing. Just fine. My opinion only thou

 

Airbags will affect the ride less. But they won't help your axle shafts stand up to the weight.

If you load your trailer right, you should have about 15% of the trailer weight on the ball. So 4500 pound trailer should be about 675 pounds on the ball - if your bed isn't full of stuff it shouldn't sag it too much.

 

By buying a RAM 1500 Crew Short Box 5'7" (5.7L VB HEMI) using it in Switzerland shall I ask before purchasing to increase the payload capacity in order to reach GVWR 3.500 Kg or shall it be done even later?

 

What year truck? I suspect you are in the wrong section. No hemi's in 2nd gens.