*Run him over* and *run over him* have distinctly different nuances for me. *Run him over* has clear and malicious intent (to damage with a vehicle) *Run over him*, absurdly, admits the possibility that it may be for his own good/enjoyment ... (a simple description of an action, without implied intent) So, a 'bad guy' will try and run someone over. A 'good guy' may run over someone by mistake.