Your truck will probably weigh close to 8800 to 8900 lbs with passengers and gear. Subtract that number from the GCW on your door and that should give you an idea on allowable weight. Just be careful not to exceed RGAWR. Some toy haulers have really high pin weights that can put you over RGAWR. I talked to editor at trailer world last week, he did not have nice things to say about Keystone.
2013 GMC Sierra 1500 Crew
2003 LB7 ECSB 4X4
LT265/75R16 Michelin MS2
Senior Development Engineer
General Motors Milford Proving Grounds