We tried to get into Rafter-J (based upon recommendations on this forum) but it was booked. I like its central location and that it was set well back from the road (i.e., quiet). We stayed at Custer Gulch. It is just out of Custer, SD so it is not centrally located. Travel times will be greater than R-J. It wasn't much time or distance to get to Mt. Rushmore, Crazy Horse, Jewel Caves, or Custer State Park. It was a drive (but a beautiful one) the day we drove past Pactola Lake onto Deadwood, Spearfish, and on to Devils Tower, Belle Fourche (geographic center of the USA...yep been there...got the picture), Sturgis and back. That said, this loop would have been nearly as long from Rafter-J.
Custer Gulch will hold a rig your size. There is ample space between camp sites, and it is set back 400 yds from Highway16A. It was a very quiet CG. We didn't use their showers or washing machines, so I can't comment about these.
When we return to the area, I will try planning better and book Rafter-J. If I can't reserve there, I wouldn't at all be disappointed returning to Custer Gulch CG.