Probably not.. there's usually scammy strings attached for all that excess money that will be supposedly be sent to you ala rubber check.. with instructions to send the excess to someone else of course and you get to keep some extra supposedly for yourself as well. No one in their right mind wants to pay more for a truck then what is being asked, usually real people want to bargain and dicker price IRL!
If he's emailing, then you can report those here:
Internet crime report:
http://www.ic3.gov/default.aspx