We have stayed at Big Meadow and Loft Mountain in our 40'.
It's a boondocking experience. No hookups of any kind. While you can get a big rig in there, the parks weren't designed for them so it pays to be patient and have someone outside looking out for you as you enter your site. Lots of trees! I don't think I've tried to put my rig into tighter sites than what I have found there.
I don't do first-come first-served situations, so I tend to lean towards Big Meadow as there are more reservable sites there.
2005 Newmar KSDP 3910
ISC on a Spartan