Stand alone ignition off the CAS should do the trick. Other option is a trigger wheel off the crank. Meh, I'd be happy getting it set up on the SOHC to be honest. I'd need to knock the valve guides out of the head I've already ported and take out the shrouds to maximise flow. Then design an air plenum to duct an air charge from out of the engine bay. Monkeys might fly out of my butt too...