What springs do I need for the rear 2.5" or 3"?

[Dodger009]

I'm actually asking this question for my Sister-in-Law.
She wants to get either Helper springs or an Add-a-leaf for my brother.
He pulls a 6'x15' enclosed trailer load with Racing ATVs and Equipment.
The load with trailer is about 4500 or more. But that is a total guess.
The rear of the truck sinks at least 2-3" with trailer.
I understand this shouldn't be a problem. But it has a torsion key leveling kit and now the front point up
and the rear lower.

My brother has a 2005 Dodge 1500 4-Door. (MegaCab?)
With 5.7 Hemi Engine.

When looking at helper springs it ask me if I need a 2.5" kit or 3" kit.
What dioes he have or how can I tell?

Here is the link to the kit.

2003-2008 Dodge Ram 1500 Pickup 2wd 4wd - 3500 lbs Helper Springs - LP-35 [Progressive] (pair) - 3527 | $324.95

What kit will we need? And would a 2,500 or 3,500 lbs kit better?

Feel free to add your opinions on Add-a-leaf if they don't raise the back up much or require longer shocks.

 

[xb1230]

If the truck sits well while not towing or hauling, you could get a set of air balloons. They can be adjusted based on the load and maintain the truck not only level, but also a comfortable ride in all situations.

If you add helper springs, they are there even if you are not hauling, and the truck's comfort will greatly suffer from it.

 

[NWRQC]

Firestone ride rite air bags will do the trick. They won't raise the rear when aired down and the truck is unloaded, but they will level the rear and provide ride control when towing.