I have a 2012 RX350 that was rear ended.
Body shops and their insurance have deemed it a total loss. There's no structural damage. It still drives fantastic.
What's the best way to show them the real value? Assuming they try to pay out as little as possible. I was planning on compiling a list of similar vehicles for sale and to use that. I'm not sure if there's a specific website or even an appraisal in person, if it costs $100 or so, that's fine.
I am interested in keeping it though. I know someone who wants it and we'd just replace it.
Show them NADA book value and pray they agree with it. Otherwise, convincing an insurance company is not easy and you bascially stuck to whatever they offer. If you want to take things a bit further, you can also call some lawyers in your area and ask them to see if they have any legal advice for you.
like you said, find classified listings for similar vehicles.
You could also try getting your own repair quotes from accredited body shops.