It would be best if you go to this link
and look at the description of the different parts.
That is the
2. Knock control- ESC-electronic spark control. this sends the signal from the Knock sensor to the ECM to reduce the timing if it hears a ping.
It is part of the factory GM system but is not required when doing a conversion.
For timing control you need a distr with a magnetic pick up to trigger the
10. Distributor/EST-electronic spark timing- Also know as the ICM-Ignition control module. For FI you will need to decide if you want a complete conversion (fuel and timing) or partial (fuel only).
For fuel and timing you will need a distr with a magnetic pick up. You have 2 choices.
a. The duraspark conversion. DS Distr conversion has the EST mounted external on a sheet metal heat sink.
B. The small cap EFI distr. Small Cap EST is mounted internal. This distr is made by grafting a GM upper onto an IH lower distr by a machine shop.
For the fuel only conversion you will retain your stock distributor but will need a special filter to run between your ignition and the computer.
Which then sends the distr pulse to the ECM and then receives the timing signal back from the ECM and fires the coil and the correct time.