The Black Hills National Forest does not do like other government lands and have designated 4 wheeling trails. What they do is allow vehicles on certain forest service trails. Some of these trails can only be seen by wagon wheel ruts full of grass. They are not well traveled trails as such. Every year they put out a map of trails that can be used. With all the mining that went on in the Hills there are miles of wagon trails and logging roads etc. None are developed as a designated trail.
To map you out a route I would have to get a new map and see what is open in 2010. There may be a way as a group to be allowed primitive camping in some areas with fire pits. Fires are only allowed in pits. The forest service leases the land to ranchers in the summer so don't be surprised if you have cattle in you camp in the morning.
Just to let you know its snowing there now. Some trails will be washes out this spring but ok by the dates you are looking at.
So you want 2 or 3 days broke into trips with a return to the main camp at noon? If I can get you into the Castle Peak campground (trees are restrooms) you would be 30 miles from Lead/Deadwood and 15 from Hill City, they both have plenty of motels but again it is their busy season so be wise and book rooms early. There are paid campgrounds around that area that cater to campers that want water, sewer and electricity. Your nearest fuel and groceries would be about 15 miles away in 2 directions.
I daily drive our Samurai and trail ride it too. It is our only vehicle at this time so I understand fun trails but no damage if possible.
As to the Badlands I know some private land owners in the area and may be able to get a campground set up in that area. The BLM used to allow the Black Hills 4-Wheelers to have Baja style races in the Badlands but it has been years. There is a KOA close to the area and a small town of Interior with a bar and convenience store. Wall would be 20-30 miles away and has motels, restaurants etc.
If I could present a proposal to the head Ranger of the Badlands National Monument of a group of adult, responsible folks in small four wheel drives that are going to leave the land as we found it we may be able to work something out for land use. Since your vehicles are "collector" (don't want to tear them up) type vehicles that may go a long way to prove you will tread lightly.
I know this is early and a guess but how many rigs, people, tents, camper/motor homes are we talking? Forgive my ignorance of your groups size.
or put it this way in general numbers
# of rigs on rides
# of total group
# that use tents in a primitive site
# of motel rooms needed
# of full service camp sites needed
I just need a general idea so I can help find you folks something you can use and enjoy.
Kelly