How large? Except for the smallest parks, most all have at least a few sites suitable for 40 ft rigs. Especially if you are looking strictly at full hook-ups sites.
Most any camping guide or website, e.g. Trailer Life/Good Sam. Woodalls, or Allstays RV (smart phone app).
There is a guide called Big Rig Best Bets, but I've not found that it has any advantages vs others. It has fewer listings and misses a lot of perfectly acceptable campgrounds.
http://www.big-rigs-rv.com/Home.html