With my setup (see sig) I'm using Monroe Load-Adjusting rear shock absorbers (shock with coil spring integrated). They are reported to add 1000lbs of resistance. They ride stock unloaded.
When I drop the 870 lbs of tongue weight without WD hooked up, my truck sits with a very slight forward rake. Front wheelwell dimension goes from 36" unloaded to 36 7/8". Rear drops about 3 inches.
When I engage my WD front goes back to unloaded 36" dimension, rear goes to 1" below unloaded.
Absolutely no porpoising and a great ride.
If I ran airbags I would have to keep a spare set with me, don't trust that system.
Tuftruck also makes a range of HD springs for the Ram that have had good reviews.
At $89 shipped and super easy installation I went with the shocks. One less thing to worry about. Your mileage may vary.