i installed the crane hi6 unit. it is a similar concept as the msd 6a. the hi 6 uses multiple sparks at low rpm, and switches to a hotter single spark at high rpm. it also has a built-in adjustable rev limiter, where as in the msd unit, you have to buy separate rev limit modules. i also have the crane optical trigger, and a crane ps91 coil. you can try summit racing.
http://store.summitracing.com/main.asp