I have a 91 GT with a 347, aluminum GT40 heads, Trick Flow intake, 4 core Northern aluminum radiator, dual black magic fans, 180* thermostat, stock water pump. The car runs fine and stays right at 180* unless I romp on it a few times, then it starts to overheat. Someone told me the stock water pump might not be flowing enough for the big aluminum radiator, could this be the case. Someone also told me I have a blown head gasket, if that were true wouldn't it be overheating just sitting and idleing, or under normal driving conditions? Any help anyone can give me on this would be great thanks.