Dealers will usually want leads with high-intent customers looking to sell their cars. In this market especially, dealers need to be able to buy direct from consumers. Auction prices are still of the charts. The problem with these leads is that most people are testing the waters on their current vehicle and intent to really sell is low. % of conversion is usually low, so your ads must be efficient to make sense. If you can find a dealer/client that gets this, it's a cool program to run.

Ideally they have a website + inventory feed, but you can always wing it and import a dozen cars manually and run ads to prove it works.

Perhaps you could get the content route going. The biggest issue with out of state/country is trust. Content/Video is the best way to build trust, so this one of the techniques you could use to make it work. Plus, it's much more scalable than CC/WI.

Definetly Social Media ads vs Google in this case. You can leverage emotion in a better way through images/video vs Google. Much more potential drawing people in with a low-ticket offer on social. Plus you can filter by interest, brand, etc... Technically you can do this with Google, but you'll have to wait on them to search vs. reaching out as many people possible with engaging SM ads.