I am running a Monolith campaign using Gradient Descent! Virtually everything in GD is system agnostic, with the exception of Sanity stat (we're using Willpower) and Stress (we're using Fatigue). We opted to not track the Bends stat introduced by GD—it is a cool mechanic though!
It's easy to adapt the Sample Bestiary in Monolith to the encounters in GD, but I recommend going through the Armory section and creating a couple variations of the different encounter types ahead of time.