You are really covering a lot of territory and as you rush thru, you are missing some great and interesting sites. It is not doing justice to the Black Hills. Custer SP, Rushmore, Crazy Horse only scratch the surface. Spearfish Canyon is a great ride and you can spend a day stopping for photos and just seeing the sites in it. Some of the back roads in CSP is where you really see the wild life, from buffalo, to elk, deer, antelope, (if you are up early you may see a mountain lion) big horn sheep and mountain goats up near Sylvan Lake.
If your heart is set on Yellowstone and spending a lot of time there, then forget the Badlands and Devil's Tower - although both are pretty spectacular by themselves.
Cody is a great place to visit and stay a few days, getting there over the Big Horns will be an interesting experience. Make sure your brakes on both truck and trailer are in good shape.
Have a great trip, wish we were following you across
