As far as GVWR, you will be hard pressed to find any full featured TC (hardsides, full bathroom, etc) that won't put you over on gross weight unless you go pretty small.
THE FIGURE that many of us go by is axle weight, which is determined by tire capacity.
In our case we have 7940# axle capacity front and rear by changing tires.
BTW, our truck handles the 855S really well. Changed tires and added rear Timbrens and a BigWig swaybar.