My friend was explaining to me how (according to his experience) the type of direct drive fans that are stock on my BMW ('82 320i) can be a real power sucker. Is this true? I'm looking to rebuild/replace the engine in my '82 320i. Is it possible to replace the stock fan with a clutch or electric fan? I'm looking to squeeze as much power out of this engine as I can. If I get a chance to replace it I may try to replace it with an engine from a '77-'79 320i. Any negatives as to that kind of swap?