The MS will trigger the spark with the VB921, this is it's output.

A pullup will be in the input circuit. The original MS is setup for either a set of points,(using the Opto isolator) or a VR sensor.

Mitsubishi uses a simple trigger for switching the timing events, this provides a rather clean signal especially with a shielded conductor. The MS2 has a 1K resistor on the processor pin used for the input so not much other conditioning is needed. So you can get by with a wire from the 37pin connector to the processor and install a pullup so the Dizzy has something to switch.