My 2011 Sierra 1500 has a 1420 lb payload
It is Crew Cab, 4x4, SLT (sunroof, running boards, fog lights ect) and it all adds weight.
To the OP, I would not sign for the new truck until you see the actual door sticker and calculate if it will meet your needs.
My Sierra has the 5.3 / 6spd / 3.42 gears and I run with a fully loaded trailer of 6006 lbs (weighed) and it is at the limit of my payload. Engine and transmission handle that weight flawlessly with tow/haul mode on and limiting the use of overdrive