Not sure on the numbers of the fans, but as far as I know there are two types, one for AC, a thermostat clutch and one without AC as my 69' 340, Dart has, without AC. I would think the AC one should be set a given distance to record the heat and the non-thermostat one, set a couple inches from the radiator, with the blade just to the outside of the shroud, so to grab as much air as possible thru the radiator. To close it would pull most air from the center.
