Most likely the axle has a rating over 9000 lbs, but the suspension and wheels will be your limiting factor. If you are set on getting this toy hauler look into the 19.5" wheels which will give you over 8000 lbs of wheel capacity on the rear. The truck will most likely squat under that weigh and SuperSprings or other suspension aids would be required to level you out.
Watch your GCWR - You will easily add 3000 lbs to the toy hauler once personal items, toys and water are added. I was about 4000 lbs heavier than dry when I had mine filled with toys and water for a long trip...