My 4x4 Chebby 2500 tips the scales at 7250 pounds or so. Why anyone would buy a truck that can pull/carry like one of these things can and put car tires on it :wack:
Last I got tires on my truck Discount would not mount car tires on HD trucks....
The reason Discount wouldn't put P-rated on your truck is because of liability. Like I said, overload a P-rated on the *** and the sidewall flex will make it feel like you're on ice. Loose it in cornering, spill your contents, have the truck come around on you and into oncoming traffic, and someone is going to sue the tire shop not educating the customer on what his truck really should have.
Like I said: there's a reason the factory puts E-rated on the truck from the factory. You buy a 3/4 or 1 ton truck, chances are you're gonna work it. Even half tons come with C-rated tires.
In the case of a heavy truck like yours those 8 plies make a difference, even from suspension weight. Throw a full load in it or pull a trailer and having 80# of air pressure make a huge difference over 4 plies and 35#-40#.