A great resource is
www.rvparkreviews.com. This is an online resource where WE get to review parks we have visited and make comments. I use it quite often when trying to find a park in an area that I'm not familiar with.
There are reviews on probably most parks around country, and although not specific to motorhomes or Big Rigs in particular, the advice contained there can at least tell me when to avoid a park.
I use it all the time, along with Big Rigs, but unfortunately, Big Rigs hasn't visited everywhere.
Ray