Craigslist is the obvious choice for private party sales.
Since you asked, you prolly don't know anything about CL.
Nothing wrong with it, but just don't respond to weird inquiries or too good to be true deals.
You'll have to deal with a few flakes, but that's not a huge deal. Just don't fall for scams.
To be safe, only person to person deals and verify funds.
If the buyer can't roll with cash then I wouldn't do the deal anywhere other than at THEIR bank.
You'll get less flakes with an expensive truck and RV.
IMO sell the RV first unless you get a pkg deal buyer. Truck will sell in 5min anyway if it's good shape and not out of line in price.