You have several options for dealing with the extra plug:
* Disconnect and tuck it away: This is the simplest approach. Carefully disconnect the wires from the plug. Tape the connector and wires securely and tuck them out of the way so they don't short or get damaged.
* Cap the wires: Instead of just taping the wires, you can use wire caps or heat shrink tubing on each individual wire to ensure there's no risk of shorts. This is a slightly safer option.
* Remove the connector completely: If you're comfortable with some basic wiring work, you can carefully cut the connector off, ensuring to seal the ends of the wires appropriately. Again, heat shrink tubing is recommended.
Important Note: Do *not* attempt to connect the wires from the old module to your new HEI distributor. This will likely damage the HEI and/or your vehicle's electrical system. The HEI distributor is a self-contained system and doesn't use those external connections.
Always double-check your wiring diagrams for the HEI distributor installation to ensure everything else is correctly wired before starting your vehicle. If you're unsure about any aspect of the installation, it's best to seek help from a qualified mechanic.