Can I use a different crank sensor (e.g. an automotive inductive sensor with a 24-2 wheel) instead of the original pickup?

Ignitech recommends using the original pickup system when possible. If you use another sensor, you must specify exactly whether it is inductive (2 wires) or hall effect (3 wires) and the trigger pattern (e.g. 24-2, 60-2, single lobe), because the unit's input hardware is built for that sensor type.