The 1500HD *IS* a 3/4 ton truck.
A light duty 3/4 ton, but a 3/4 ton nonetheless. 8-bolt hubs (on a semi-floating axle unfortunately), 8600lb GVWR, 6084lb RAWR.
It is a far more capable truck than a 1/2 ton, but far from a "tow anything" truck.
As I recall, tow capacity with the 4.10 gears is 10,000lbs. That will really be your practical limit because the pin loaded weights on 5th wheels at that size will be pushing 2000lbs. Add a hitch, you, and a couple passengers, and that ~2800lb payload is pretty much gone.