I agree with Jim in the points he made, but would strongly discourage you from doing it. The part I would worry about isn't pulling, but stopping almost 16,000 lbs ((6400+9000)+ anything including you inside the H2). moving at any speed much less 70 mph.
I'm sure the engine has the power to get that mass going, but the brakes having enough stopping power I'm sure will be quite another matter.
Oh, btw if you have an accident overloaded, kiss any insurance coverage goodbye.
Bottom line is that if your load is that big, please, for your own safety and others; get a different truck. You will be much safer and live longer.
