the controllers in those takes a pulse reading based off resistance, selected by the switch for different pulse settings and assuming 4 stroke with no wasted spark (i.e. a 4 cylinder throws 2 sparks per revolution, 6 -> 3 etc.)
so you'd just need to switch the resistor for any one of the positions (or use a variable resistor) to vary the resistance to make it read properly at 1 spark per revolution.
probably a 1/x relation?
I feel like you will be the one to figure this out. but you could measure resistances for the different settings and get a trend of resistances vs pulse/revolution and extrapolate down to 1 pulse per revolution