When considering what tires to purchase for your truck, think about the load carrying capability of the tire you select. Half-ton pickups can use standard load-rated tires, but 3/4- and 1-ton vehicles require load range D or E tires to meet the Gross Vehicle Axle Weight.
For example, a common truck tire size of 245/7R16 is made in standard load, load range C, D and E but can support distinctly different loads and accept considerably different inflation pressures.
Maximum Load: 2,271 lbs.
Max. Inflation Pressure: 44 psi
Load Range: SL
Maximum Load: 2,205 lbs.
Max. Inflation Pressure: 50 psi
Load Range: C
Maximum Load: 2,623 lbs.
Max. Inflation Pressure: 65 psi
Load Range: D
Maximum Load: 3,042 lbs.
Max. Inflation Pressure: 80 psi
Load Range: E
As you can see, the load carrying capability of the tires varies greatly and is designed to meet the needs of the heavier 3/4- and 1-ton axle weights when you get into load ranges D and E.
Meeting the load requirements of the vehicle you are putting tires on will offer you the safety and performance the vehicle was engineered to provide.