If you want a programmable ignition system only, then the Megasquirt is a waste of money.
Megasquirt is the full efi and ignition system (and a very good one in my opinion).
There is a smaller version called Megajolt - which is ignition only.
It utilises the Ford Electronic Distributorless Ignition System (EDIS) which is a wasted spark system (fires 2 cylinders at a time).
Not sure how to configure a 3cyl eng, but 4, 6 & 8 are fairly easy.
Probably use a 6 cyl version and fire only 1 cyl at a time.
Some info can be found here:
http://www.autosportlabs.net/Main_Page
I looked at the Jaycar kit a few years ago for the dual map feature for dual fuel.
Turned out to be a bit ordinary.
It only had 3 set points to "map" a curve. Fairly useless!
I'm not sure, but I think it has improved since then.