Not all sites in Stockade North and South have electric and water - none sewer. This may have changed in the last few years but I doubt it. There is one dump station a Game Lodge and none on the west side of the park. I don't know about Horse Camp.
There is/was a dump station in the town of Custer at the truck stop on the west end of town near the liquor store.
While CSP is a beautiful place to visit and camp, basic amenities are lacking.
We worked there for two years as a host at N and S Stockade CGs