While I have a "short" fifth wheel, it still has at times been "interesting" to get into state park sites that should have fit. Take their notes about the pad length seriously, and use the total length of your TT and TV. Harder is getting an idea of the surrounding conditions. I've been in places where the site is big enough, but it is a narrow one lane road past the site, and close to the opposite edge is a wall of brush. Making turning and backing, as I said, "interesting". Check out the surrounding sites, as well as pictures at Campsite Photos, Camping Pictures, and Campground Reviews - campsitephotos.com
to get an idea of what it may be like, and pick accordingly.
One private place we were at for almost two weeks was Stoney Point Resort, up north on Cass Lake. Minnesota Family Resort - Camping, RV Park and Cabins on Cass Lake, MN - Stony Point Resort
Well kept place. Huge swimming beach. It is mostly seasonal, but there are a relatively high number of by-the-day sites. All are pretty spacious. Good restaurant on premise. Right next to miles of paved bike trails. Easy access to several state parks and recreation areas. About an hour or so to Itasca State Park (where the Mississippi starts). 1/2 hour to Bemidji. Boat rentals available for fishing on Cass Lake. Premium sites even have their own docks!