Outer Limits 4x4 Board

Is there any way of getting a stock tacho (specifically out of a sierra) that ran off the coil to destributor (G13A), to work with a coilpack ignition engine (G16B)? I ask this in here as it would apply to many different vehicles.

I've seen systems modified by picking up the coil primaries of the multiple coilpacks and wire ORing then via isolation diodes to the tacho.

The tacho then see's the pulses from both coilpacks. Diodes of an appropriate PIV should be used - current rating is virtually irrelevant.

Of coure the tacho could also be modifed electrically or mechanically to read correctly with half the input pulses ( ie one coilpack ) but i rather like the diode idea.

Note.... I've seen it but not done it so this is more of a concept.

Do you know if the ECU steps up voltage to the coilpacks or would i be safe using say the good ol 1N1004?