GPG52!, there is an easy answer to that question, they simply post the Manufacturer's towing numbers which is what it can pull not what it can carry. People also look at the listed "MAX" payload, but buy a option loaded TV, which sometimes greatly reduces the payload.
No weight police as I am well over the 8,800# GVWR of my 2001 Ram CTD 2500, but still well under the stock 6,084# rear axle rating. If I wanted I could base on tire capacity which is what stock rating is based on, with the optional 265's I could go to 6,830#.