I don't mean to point out the obvious, but when calculating the load capacity of your tires don't forget to take into account the empty weight of the truck itself that the tires will be supporting.

Example: E rated tires can support 3415 lbs, times 2, that's 6830 lbs. Subtract the rear axle weight of your truck (not sure what that is, let's say it's 3000 lbs for simplicity). 6830-3000 = 3830 lbs you can add to the rear of your truck.

I think this makes sense, let me know if i'm all wet. Again not trying to be a smart butt, just wanted to point this out. .