my GMC 2500 tow vehicle ..

edstep wrote:
I currently own a 2011 GMC 2500HD, 6.0 gaser with a 3.73 rear

I am looking at a new trailer, the documentation on my truck says I can tow a 9500 lb trailer ( unloaded) the new trailer that I am looking at has an empty weight of 10,856 - 11169. The pin weight for my truck is 2500.
The dealer tells me that my truck would be able to tow as you can tow more weight towing a 5th wheel rather than a regular TT. I have heard this before but I need some further input

Pure BS from the dealer. He just wants to make a sale.
In fact the reverse is often true - due to pin weights being higher than tongue weights of a bumper pull it is often the case that a given truck can handle a heavier TT than a fiver.
Ask him to put in writing that you will not exceed any of your truck ratings with the fiver he wants to sell you. Then see how fast he back pedals!

Reality is that you can tow 9500# MINUS any weight you add to the truck other than a 150# driver.
What do you mean by the "pin weight for your truck is 2500#"?

If you mean what you can carry in the way of a fiver pin, then that could be close. It depends on your truck configuration (cab, 4WD, box length, options etc).
To get a real number for your trucks pin capability........
Read the "Tire and Loading Information" label on your drivers door pillar.
Subtract all weight you add to the truck from the Payload rating from that label.
What is left is what you can add in the way of a hitch and LOADED fiver pin weight without exceeding your truck ratings.

BTW, an 11,000# empty fiver will be 13,000# plus once loaded, with a pin weight around 2600#. Add 200# for the hitch.
You don't have enough truck for that.