It must've really bugged GM to see Ford own the luxury heavy-duty market, especially considering that GMC's Denali line has been known for truck luxury since 1999. When General Motors announced it was expanding its Denali line to include heavy-duty GMC pickups, it made perfect sense -- this could be the way for GM to battle the King Ranch in this segment.
For a lighter-duty vehicle, creating a Denali version is relatively easy: Add chrome, offer Denali-unique wheels and tires, and Denali-specific interior cues, and, in some cases, make a larger-displacement, higher-horsepower engine standard. Look at the Yukon and Yukon XL Denali. In addition to the Denali styling upgrades, that trim level is the only one where you can get the 403-horsepower, 6.2-liter V-8.
In the case of the 2500HD and 3500HD, though, creating a Denali package is more complicated. At the heavy-duty truck level, styling and wheels are nice, but they can't have a dramatically negative effect on the truck's capability. The Denali package is available on 3/4- and one-ton heavy-duty trucks, crew cab only, with either rear- or four-wheel drive. Denalis come with the standard (6.5-foot, 2500HD) or long (8.0-foot, 3500HD) bed.
How do you know it's a Denali by looking at it? The truck, offered only in black, gray, or white, has a four-bar chrome grille, chrome accents, and 18- or 20-inch polished forged aluminum wheels on the single-rear-wheel models, 17-inchers on dualies. Interior amenities include a Bose audio system, power-adjustable pedals, brushed aluminum accents (unique to the Denali), and 12-way power seats. Heated steering wheel and heated/cooled leather seats are options.
Other than those differences, the rest of the truck is exactly the same as the standard Sierra HD line. Unlike the other vehicles offered with the Denali package, the Sierra HDs come with the same engine/transmission pairings; the 6.0-liter V-8 and 6L90 six-speed automatic transmission is standard, and the 397-horsepower, 765-pound-foot 6.6-liter Duramax turbodiesel V-8 and Allison 1000 six-speed automatic are an $8395 option. We would've liked to see some differences between the Denali engine and those in the rest of the heavy-duty line, but there's certainly nothing lacking here. Besides, Ford has the same philosophy with its King Ranch Super Duty.