I had a 3.92 and it was great with my 6500 lb travel trailer loaded. I had the big gas tank also. So, my old one gave out and they still offered me 21K after 75K miles when they only offered me 15K about 15 or so months ago.
A built to serve was on the lot being looked at by more than one person while I was there still waiting on the verdict for my 2015 Outdoorsman. It checked every box except it had the 3.21 gears including the tow package, off road package and it is essentially blacked out and had more than what I was looking at 15 or so months ago. My goal then was to get one for about 35K. So, I dithered and that evening saw this video by TFL with a FULLY loaded 3.21 5.7 and said, OK...
https://www.youtube.com/watch?v=yWf8L2g9Z4I
I do about a 500/600 Hundred mile first tow this weekend, 100+ degrees at the destination and 250+ miles each way one pass and then down into spokane WA. So, here we go... Oh, in the video, the RAM beat the latest greatest Ford F150 too.