the chin spoiler is a very important part of the cooling system om a modern auto it forces more air through the radiator. when the system is set up right the fan actually does nothing above 35mph or so. yes the t stat is also required to slow the water flow through the radiator so it cools. also make sure your heater hoses are at least hooked together most V engines need that flow to properly remove the air from the heads, if the heads have no water in them no cooling of the enging. i had a project once where i put a 455 olds in an 80s toronado and i actually had to add a larger chin spoiler to keep it from overheating at 25mph.