If you look at the GVWR of 18K and take 15% and 20% your pin weight can be anywhere between 2700 and 3600#. I am not the weight police by any means but that would be way over weight for my 2006 F250. The F350 has about the same towing capability but can handle more in the bed. If I had to purchase a new truck I would look at nothing less than a F350 but would go to a F450 if you can.
My BH has a max of 14800. We travel full time and I am at the max my truck can pull. I don't have any additions on it yet.