What is the problem with the ride? Too stiff and rough? Or too much bouncing?
Being a 3500 I would have to guess that the ride is very stiff. If the van is only loaded with a few hundred pounds, the ride is going to be rough for the dogs. I don't see how airbags would help that. If anything, they will stiffen the suspension and make the ride even rougher.
If you have a lot of weight and the suspension is wallowing a lot, causing car sickness, then bags might help.
The type of hitch can make a difference as well if they are only getting sick while towing. The small amount of swaying and bouncing caused by a tt will bring on car sickness. I had a friend with a daughter who got sick every time they towed the trailer, no other times. They used a passenger van too. He bought a Hensley Arrow ($$) and problem solved, she never got sick again.
