Yes Custom Differentials 4Wheel park is open on all weekends except event weekends. You need to call Jeremy at 573-483-3343 and ask for details and he'll hook you up with all you need to know.

  Also there is a place south of Potosi Mo that's called Palmer Lake. There are plenty of trails--mostly mild but plenty of them anyway. Also there are lots of different mud holes and hill climbs that range from mild to wild. It's part of Mark Twain National Forest and trail maps are available at ranger stations in the area for $7 each. There are 3 main lakes to swim and fish in too. I don't have exact directions for you but I have wheeled there for years with every thing from buggies to big 4x4's and had a whole weekend of fun.