So far this is what I found for a complete kit for lowering the Denali Magnaride.
2" rear
http://www.mcgaughystore.com/2015-2017-gmc-sierra-denali-1500-2wd-4wd-2-rear-leveling-kit-prs-152l/
2" front 4" rear
http://www.mcgaughystore.com/2015-2017-gmc-sierra-denali-1500-4wd-w-magnaride-2-4-deluxe-leaf-drop-kit-prs-sd24-4wd/
Socal