I'm not sure this answers the question you have and seems to disagree with most of the opinions stated above. I have a 67 Barracuda Formula S with the factory tach. I have a Year One "replacement" engine harness for 67 cars that have added electronic ignition. I snapped a couple of pics and you can see the grey/w blk tracer tach wire exits the bulkhead connector at the bottom and is "sistered" with one of the leads for the ECU. Sorry the pic is sideways...... dang it!
