there are acouple of cheap EI products out there but since you have to get rid of the flywheel and get a replacement prop adapter to fit the taper its going to need more than just the ei. its doable and would be better but it wont give you more power. also look for some locktite gasket maker or some red rtv and get rid of the gasket between the head and the crankcase it lowers the head and increases compression a bit will give you some more rpms. becareful not to get the red rtv or gasket material in the engine. If it hand starts with ease I would leave it alone. try bringing your prop down to a 18x6 and see if you cant squeeze some more rpms out of it. I used top flite on mine.

edit: CH igitions has a kit with ignition pick up hall censor magnet and prop adapter with the back taper to replace the fly wheel spacing.
http://www.ch-ignitions.com/#cat