Sorry for the lateness of my reply. Just now seeing that I was tagged after finishing giving my rig an oil change.
@1xd5 Looking at the photo of that red Denali xl that you posted beside your truck and reading the thread that you linked, it appears that the owner of that truck didn’t just swap out the factory torsion keys for leveling keys to achieve enough lift to fit that tire setup. There’s mention of Z71 coil spring swap, which lifts the rear of the truck up for sure, from what I’ve read on others member’s lift threads here. The thread also mentions rough country shocks so I’m assuming longer shocks were necessary. Doesn’t say what shocks but I’m guessing he deleted the Z55 suspension setup with the rough country shocks.
So quite a bit more in depth since leveling keys alone won’t lift the truck enough to fit that big of a tire on stock suspension. To also add to the info in this thread the factory does setup a mild rake to the suspension. At least with the GMT800s they were definitely not level out of the factory. The front is set a tad bit lower than the rear, from what I understand to help with aerodynamics and fuel consumption. I can say for certain this is how my truck was setup on stock suspension.
The leveling keys will lift the front of the truck a tad bit higher,
I did that to my 2006 Denali xl. Not sure what brand keys were used but it brought up enough to fit a 275/65 Michelin LTX A/T2 tire on my truck a couple years ago. Running a different tire setup now but still have the leveling keys.