An ex-boyfriend 'gave' you some money, so you could argue that, at the time, it was given as a gift. Considering that there is nothing to suggest that this is his money, that it was intended as loan and that it has taken eight months for him to come to you about it, I don't think he has much of a chance of getting this money back or the car instead.
But then again, put yourself in his shoes. If you had loaned money to a partner and then split up, you too would want to get it back, wouldn't you?