Maybe 1500's.
Wife is not happy with the drone in cab. She has not said anything about it for 15 years..now it is an issue. Truck is loud, especially with a load.
The air ride on the 3500 is not a four corner system like the 1500 and the suspension is different from the 2500. The air ride on the 3500 is more of an "auto level" than anything. Think of it as an automated integrated airbag system. When dropping my 5'er on the 5th wheel, it sacks out the rear suspension by a good 2-3 inches. Im looking to level it back up when hitched up. It will tow just fine this way, albeit a bit "nose up".
I have around 3600 pin weight on my 2015 SRW 4x4 and do not feel a need to add air bags. I would think a leaf spring duallie would hold up to its RGAWR without help, as it is not a sagging Ford!