The biggest rig we got coming size wise are some Early Broncos. Unfortunatly full size trucks have a hard time on the trails. There is a big quarry area that the full sizes do play in and I have seen a couple full sized trucks/Broncos run the trails. Those guys usually end up with some nice pin stripeing.
There will be some open seats for those that didn't bring trail rigs. The park is very ATV friendly also, if you have one.