I just made that swap this weekend, going from a 2014 2500 6.4L with the coil spring, to a 3500 Cummins. Both are SRW short beds.
The 2500 did ride better, but the difference was not as dramatic as I expected. The 3500 is not the "crashy" lumber wagon of one-tons from years ago. It's stiffer for sure, but still pretty well composed. Then again, I've had it for only three days, and haven't hit the worst local roads yet. Final outcome still pending.
But it IS worth trying both out. So far, I've been pleasantly surprised. Hopefully that impression holds up over the long run.
