When we went shopping for our current TH and nearly a dozen local dealers told us we could tow anything on their lot with our Chevy 3/4 ton gasser. The only dealer that was straight with us on our TV's actual towing capabilities is where we made our purchase. From my experience most dealers and their sales personnel just want to make the sale placing many in uncomfortable towing situations.
We actually were very near closing on a rig from another dealer that would have put us at least 1500# over and that's without toys and water. Wanting to be thorough we went and visited the last dealer in our area with TH rigs on the lot. Thankfully we did and the first thing their salesman told us after inspecting our truck is that he would only show us rigs we could safely tow, first time we heard that.