Unfortunately this would be a bad idea because the car isn't his and the plate won't lead to the scammer. These guys are over seas (often Nigeria, but I had a friend also tracer some to a couple of eastern European countries as well). What they do is they rip off images and/or descriptions from legitimate ads in other areas. Sometimes you can even find the legit ad still up with a mashup search. When you do, you'll see that they copy the ad in it's entirety, but cut the price down to something like 25% to 30% of what the original was. If you do turn the plate in to local authorities, you'll just be creating a headache for some legitimate guy trying to get his car sold and I don't see any good in that.

As for the e-bay looking things they send, it's the same deal. They copy a real e-mail, but embed re-direct code. Careful playing with it John as some redirects also have other malicious code that can cause extra trouble down the line. Always, even when you think an e-mail can be legit, always type out the URL yourself in a new browser window rather than clicking on it and letting the re-direct happen. There's nothing that can be done about the scams except flagging them down when they are found, and making sure no one we know falls for them.