Check these sites out...it is a good reference.
http://www.bcae1.com/
http://www.termpro.com/articles/articles.html#How
If your headlight dims with the bass notes, the “BIG 3” might work. If not an H.O. alternator will be needed, or else be prepared to pour a lot of $$$ for batteries.
This site explains the "BIG 3" upgrades.
http://www.sounddomain.com/ubbthreads.php/ubb/showflat/Number/312025/page/1