You need to re-read Hotrod Lincoln and Crenwelge posts...
Yep, don't skimp on the air pressure.
For truck tires I usually start out at the recommended pressure on the sidewall and if lightly loaded and as needed for comfort reduce the pressure a little. Keeping an eye on how they look and wear and keep enough air in them so they always look tall and proud and never wear the outside of the tread first.
Grigg