I'm OCD about weights, my apology for the rant.
A visit to the scales will give you your current TV axle weights. The difference between the Rear GAWR and the rear axle weight will be the cargo you call add to the rear. That number (minus about 100# for a hitch) will be about 25% of the Max 5er weight you should consider (IMHO).
As an example: the yellow w sticker says Rear GAWR is 5500#. The scale says drive axle weighs 3000#. Your total cargo (hitch, pin weight and any "stuff" in the bed) is 2500#.
Assume 100# for the hitch and you are left with 2400# of cargo. Let's add 100# of bicycles, firewood and adult bev's and we have 2300# of cargo remaining. That 2300# will be roughly 25% of the Max 5th weight you should pull. In my example that comes to 9200#.
Keep in mind that the published weight is probably less than the "shipped" weight and you will add more weight with your personal "stuff". I anticipate about 1000# of stuff.
Being at or slightly over axle weight max's is not a real deal breaker but I prefer to be under.
The scale will cost about $10.
The CAT Scale is your friend.
Edit: one last opinion, the dealer will likely tell you your truck will pull ANY 5er you want (bigger the better). Do your own research on that!
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks