You have a '08 2500 Chevy Dmax/A 4x4 crew cab long bed and IMO you haven't read the right numbers.
Your '08 2500 Dmax/A is rated to tow a 14500 lb 5th wheel or a 12k bumper pull.
Your 2500 Dmax/A has around a 21000 lb GCWR.
Your quote says; "In the manual under cc long bed 4x4 6.0L V8 4.10". This isn't your trucks numbers but the smallblock 6.0 gas engine.
The only thing I see is the truck front axle is overloaded. You sure must have a lot of options and extras up front for the front axle to be over loaded (4680 vs 4880 lbs). I would suspect those numbers also.
