So we have a 2005 F350 4x4 PSD SRW CC (with the camper package) and are
planning on getting a GN horse trailer with a dry weight of 5900lbs for an estimate loaded weight of 12Klbs and a 20% pin weight of 2.4K. All the figures are within the 23K GCVWR and 17K tow rating.

Am i missing anything?

The truck should be around 7,800lbs or so (measured ounce at 8K with a shell and full tank), so that leaves me with 1,200 lbs of payload (11,400GVWR) after the 2.4K pin weight.

The trailer is 7'6" Wx7'6"W and about 33ft (includes 8 ft GN area) and most of the weight will be over the 2 7K axles (1,800lbs horse and 1,100lbs horse out of the 6K total trailer payload i came up so far). The 6K payload is kind of the worst case scenario(4h hauled...which never really happens), unless we get another draft horse....

 

You will be fine. Here is a pic of our unit. Loaded up it came in at a little over 20k combined weight with no axle or truck overloads. The trailer by itself is just over 12k. Pin wieght was about 2,400.