Just get the Crank pulley. The Water pump pulley and Alternator pulley are a PITA!!! Not worth the trouble. But if you do decide to get the 3-piece kit, throw the Alt. pulley away or use it for a frisbee or something. Besides, it's the same size as the OE pulley. But, If you get just the crank pulley, make sure you get the proper belt (if one is not included with the pulley)
I got the esslinger pulley (ford racing actually). Then got the fc water pump pully from black diamond for about $50. My main reason was to stay with the stock belt.
I've enjoyed the mod, the engine definitely revs faster. But don't expect to miracles.
I'm on my 3rd car with that setup, works very well.