Did some searching for measurements with air suspension and ran across this:
http://www.sae.org/mags/aei/12353/
"New link-coil rear suspension for 2500
In the chassis, the major change for 2014 is the new five-link-coil rear suspension system for the 2500, which benefits from lessons learned on the 1500's link-coil system introduced in 2009. Importantly for the HD segment, there is “absolutely no compromise in payload,” Mets said. “As a matter of fact, we increased the GVW [gross vehicle weight] all the way up to the class max 10,000 lb in both our gasoline and our diesel applications. ”
The system offers a 40-lb (18-kg) weight reduction compared to the previous leaf-spring configuration, Chrysler engineers claim. (See video at 2014 Ram 2500 gets 'beefed-up' link-coil rear suspension - SAE Video for more details on the 2500's rear link-coil system. )
An active load-leveling air suspension, for which an airbag replaces the coil spring, is also available on the 2014 Ram 2500. Load capacity is not sacrificed, and the load-leveling function detects load on the rear suspension and automatically increases air pressure until the vehicle reaches normal ride height.
“We wanted the vehicle to have a 1° positive grade angle—whether loaded or unloaded—for a very solid, strong look on the road,” Mets explained. “Unloaded, the air suspension is about two inches lower than the steel suspension, offering you better ingress and egress. ”
The air suspension system has two modes—normal and tow—that can be controlled via a button on the center stack. In tow mode, the grade angle is lowered to 0° “so when you hook up to a trailer, you're looking more level as opposed to pitched in the center,” Mets said.
Engineers took a different approach with the air suspension for the 2014 Ram 3500. “We actually kept the main leaf, but we softened it up, and we added the airbag [and] an upper control arm to manage the axle torsion,” said Mets.
The supplemental airbags allow for more unladen suspension movement. When a high-load capacity condition exists, the air suspension automatically fills the rear airbags to level the truck and improve stability and ride quality, including with a claimed best-in-class 30,000-lb trailer in tow.
As on the 2500, the 3500's air suspension has two modes—normal and trailer—and is optional on both single and dual rear wheel models. "
The 2500 and 3500 have air bags on the rear axle only. The 1500 has air bags on all four corners.