We went there a couple years ago in our truck/truck camper. We're around 23' long. We had the camper on the entire trip and didn't have much trouble finding places to park in the park. There was only one trailhead that is very popular that we couldn't find a spot to park.
We did go in early September so the park wasn't nearly as crowded as it would have been in the summer months.
2005 Dodge 3500
2001 Lance 1030
2006 Cougar 29RL