The rear axle is Definitely NOT Full Floating.
As for Payload, At first the Salesman at first said that you could put maybe 600-900 pounds on the GN hitch, which I was pleasantly surprised with as it was most likely pretty close to the truth. After he went back in to "re-check the numbers" he came out and said, before I showed him the sticker, that you could put 1,500-1,600 pounds in the Goose Neck Hitch.
As for the Truck it was really nice but I did forget the most important thing. For $65,000 you get a TWO WHEEL DRIVE Truck! I missed this but my buddy went so far as looking under it to make sure it was not 4x4.