I have for sale a never used aluminum lightweight alternator pulley. Lighter rotational mass means freed up HP, and faster revs. Asking $40/$45 + shipping. Having trouble uploading pictures from my iPhone, but they can be seen here: http://orlando.craigslist.org/pts/3869519015.html
I've ran lightweight pulleys on my car from 2006 to October 2010 before I totaled it with no problems at all. Yes there have been "horror" stories, but that usually comes down to who made the pulley. I've also been an automotive machinist for a living since 2008. And they can be fine to use.