ive heard so many different opinions on underdrive pulleys i dont know what to believe. what ive been told is replacing the crankshaft pulley with an aftermarket pulley causes you to remove the harmonic damper which will basically throw off the balance on the crank and none the less destroy your engine. if anyone believes otherwise please feel free to tell me. also, would it hurt to replace the alternator and water pump pulleys. they will be going on a stock d15 motor..