I have a CRANE hi-6 ignition. It is a complete kit. Everything you need comes in the kit. I have both MSD and CRANE and there is no difference to speak of. I only paid 160 from SUMMIT for the whole kit. It increases throttle response and seems to rev alot cleaner from 4500-6000. It has a built in rev-limiter. If you are running boost or alot of compression a healthy spark is a must. But are also welcome on a stocker.
Great advice from Mike. I have the MSD 6al with a Crane fireball ps 91 coil. Does pretty much the same thing Mike spoke of. I also bought the MSD distributor to go with it. So far so good. Pretty happy with the setup.