Sure glad to ......
Nivomats are a type of load-levelling shock absorber that compensate for added load in the rear of vehicles.
They have been OEM on Certain Volvo's, Jaguar XJs, Chrysler Voyager Minivans and others. They are standard equip. on the Magnum (same LX platform) with towing package, and on the SRT8
They must be fitted with the springs that they are packaged with - counter-intuatively the springs are lighter -rated than stock because unlike most other shocks Nivomats themselves support part of the load.
The only caveat - and this is just my opinion - that if your car is severely lowered because of the way Nivomats operate they may raise the rear of your car, I'd findout if the SRT8 (a factory lowered car) part #s are different from the Magnum units - if they are different I'd go with SRT8 units/SRT8 springs.
Chrysler's description of them for use on the rear of the 2006 Charger:
"This vehicle is available with either standard gascharged
shock absorbers or Nivomat™ load-leveling
shock absorbers for the rear suspension. Depending
on options, the load-leveling shock absorbers may
either be standard or optional equipment.
On the exterior, the load-leveling shock absorbers (1)
are larger in diameter than the standard shock absorbers.
Each load-leveling shock absorber is a self-leveling,
self-contained vehicle leveling system and shock
absorber combined. It does not require any external
compressor, hoses, or height leveling sensors. When
cargo or passengers are added, the load-leveling
shock absorbers use normal ride motions during driving,
even on smooth roads, to raise the rear of the
vehicle automatically to the unloaded (or curb) height.
When the load is removed, the vehicle maintains this
rear ride height."
Hope that helps, want to ask more I'll answer to best of ability