They say it will work on the 5.9 Cummins. ...
http://airflowamerica.com/?page_id=91
HOWEVER: they say ONLY for 5.7 Hemi: ....
http://www.airflowsnorkels.com/details.php?id=11
If you consider the diameter of the tubing, you will quickly understand that there is no way it can flow enough air to keep a hard breathing 5.9 happy. If you never tow and your engine is stock, then it would probably be OK. I love snorkels (I have a Safari on my 80), but there is no way I would install that on my Gen 3 Ram 5.9. A correctly sized snorkel for a Cummins would be HUGE.
John Davies
Spokane WA USA