2019 GMC Sierra 1500 Denali has a box full of wonders

GMC put a tailgate in its new pickup’s tailgate, and if that doesn’t make the 2019 Sierra 1500 Denali sufficiently meta than we’re not sure what will. The completely revamped new truck is the fanciest of GMC’s pickups, and that makes it the starting point for some of the automaker’s newest features. That includes the MultiPro Tailgate, which GMC has …