The first place to start would be with the owner's manual in the glove box. Depending on the axle gears it will not be rated to tow even 9000 lbs regardless of the engine. You need to get the gross combined weight rating (GCWR) then subtract the weight of the truck, occupants, and any payload in the vehicle to get the capacity left for towing.
Axle codes for ratio:
GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, HD locking
And remember that you need weight distribution and possibly sway control, that will be pointed out in the manual as well.
I got a 2014 1500 earlier this year with the 5.3 and 3.42s. The GCWR is 15000#, but the engine and drivetrain is a whole world different than that 2000. Pulling my 6000# rig on a 2700# trailer put me really close to max for that truck. I scaled down from a 2010 Chevy 2500HD and previous to that I had a 2006 Dodge 2500HD. This truck is competent but not as stable a platform as either of those trucks, plus the brakes and all the other hardware are obviously lighter duty.
Get your stuff scaled so you really know what you are towing. Most people do not take the 10 minutes and $10 dollars to stop by a truck scale and get that done.