I went from the stock tires rated at 3195@80 PSI to ones rated at 3750 lbs. and gained 1110 lbs. of load capacity on my SRW truck. With a DRW truck the switch would have increased my load capacity by 17% as well. If it was 11,000 lbs. with the factory tires the new set of tires would take it up to 12,900 lbs.
With the 19.5 tires there is a lot more weight and stress on the suspension components and that is not something to ignore. There is also an extremely limited range of tire treads and compounds available as these are designed for highway use and to maximize fuel economy and not for all weather or off pavement use. I would do this only as a last resort.
There is a point where you are exceeding the capabilities of a pickup truck and would be better served with a 4500/5500 class chassis cab truck.
