The listing pages belong to the big portals and that fight is not worth having. What is winnable is the seller: «sell my car», «valuation», «part exchange» — searches with intent that the portals monetise but do not own locally.
Warranty, history and finance are the three questions before any visit. A page that explains what warranty you give, how the car was checked and what finance costs answers the objection that ends most enquiries.
Each car page is a landing page in its own right and disappears when the car sells. The pages that hold positions are the ones about buying, financing and the checks you run — they outlive the stock.