Take a look at the thread on 'Scratch Built Ignition??'
http://www.rcuniverse.com/forum/m_74..._1/key_/tm.htm
A lot of great info there and several sources for complete ignitions and parts. I hope to do some testing this weekend with CD ignitions bought from marlowe and rsholl - under $100 each. Great service from both of those guys. Most all of the sources listed have glowing comments about their service, too.
Marlowe has a really good explanation of CDI on his site
http://home.earthlink.net/~marlowedc/CDI.htm
Cheers
Bill