On a 3/4 ton, I would not consider anything less than a C range tire (6 ply), even if I wasn't going to load it to capacity. While it is true the P rated Standard Load version (4 ply) of the tire mentioned has sufficient maximum load capacity, it is not designed to carry said load 100% of the time. I've seen plenty of tire failures from people using underrated tires on heavier trucks. The LT rated tires are only give a harsh ride if inflated to max pressure. run that at about 40-55 psi, they ride very well and will still handle the weight of the truck.
At the tire shop I work at as the brake and alignment mechanic, we've had a few customers come in wanting to either save money by buying P rated tires, or they want the white letter version of a tire not available in the LT, for their 3/4 tons. They always end up coming back with premature wear, or in 1 case involving a '72 C20 (whice was never loaded), sidewall failure.
