www.thecliffsinsaneterrain.com They have wheelbase limitations the trails are more suited for Jeeps or ATV's. I spend a lot of time @ Cliff's in my Jeep. I have never seen a fullsize on the trail other then BRonco's or Blazers. I don't know what you drive but if your planning on using a Ford Pickup this isn't the place for you.
YOu can also check out Badlands in Attica, IN another great place. I have seen fullsize stuff here but again more suited for Jeeps or similiar type of vehicles.
I am not sure what your into but I don't like mudding. Kind of boring give me a nice off camber tight trail or some Rocks. That where the real excitment is at!!! Mudding just causes you to come home and work to hard getting off mud. I got over mud shortly after starting to go offroading. It gets old fast IMO.