Note that the build order guide applies to a base model. The Denali's weigh more than the base model so the payload will almost certainly be lower.
Here's the order guide for the Denali XL:
www.gmfleetorderguide.com
And the one for the Denali:
www.gmfleetorderguide.com
Take the payload weights there, and substract at least 50 lbs. for a Denali, probably more depending on options you selected. So for example, a 4x4 XL length Denali would have a payload of no more than 1475, probably closer to 1400 lbs.
The biggest factors for these trucks and payload (specifically for the Duramax) are:
1. 2WD had more payload than 4WD (about 100 lbs)
2. Short wheel base has more payload than XL (about 100 lbs)
3. Options can reduce payload by up to 200 lbs for a fully decked out luxury cruiser.
4. The Chevy Suburban/Tahoe have about 50 lbs more payload than the Yukon/Yukon XL.
For reference, I have a base model LS Suburban 4x4 Duramax, payload is 1618 lbs, with bench seat middle and bench seat front row. That's slightly higher than the stated payload on the specs sheet since there are so few options. So their spec sheets do include some options.
Hope that helps.