Duraspark is another alternative. Complete instructions at:
http://www.y-blocksforever.com/forum...ight=duraspark
I have done this and use a MSD 6A box on one, and the stock Ford Duraspark box on another. Both worked great. Couldn't really tell a difference in the controller boxes. Good part is the Duraspark electronics last almost forever and if you need a part you can get it from any of the "chain" parts stores.