I run my rear tires, stock size 18" Duratrac LT E rated, at 42 and my front tires at 52, running basically empty, 2 people and the usual gear. This is based on Goodyear's published, load versus pressure chart. I used AlphaOBD to lower the TPMS threshold so I don't get the warning lights for low tire pressure. This made a BIG difference to the ride and took away that basketball bounce the tires had when aired up for a load.
I changed my 1996 2500s to Bilstiens at about 100,000 klms. It made a huge difference, if I had known how much, I would have done it when the truck was brand new. So when I ordered the new truck I ordered the Offroad package as it comes with Bilstiens. The Biltstien shocks in the offroad package are way smoother than the other OEM shocks that come on the non-offroad models.