bore tech offers and ignition system that replaces both points and the mechanical advance. it has a small computer that has to be intelligently placed to provide air flow, most practical for racing and it will cost you in the realm of $350.
there are also instructions surfacing on the web showing how to modify the dynatek ignition for a gl1000 to run on a cb450. this requires some minor fabrication and cutting/grinding on the dyna unit itself. these ignitions run about $130.
to my knowledge that's about all there is out there for a street bike.
dynatek does not believe there is a big enough market to provide an ignition for the 70's honda twins even if they made one unit that ran on all of the most popular.
If there are articles online on how to modify Dyna's to fit CB450's...
Can someone please post a link? I am really interested in doing this. Sounds about $200 cheaper than buying a dedicated unit for the CB450.