If you have an Autolite 1100 the venturi port could be plugged with expoxy or JB Weld.
If you stick a wire thru the vacuum advance port you will find the venturi port.
A 6-32 Phillips head screw will also work if you the drill the tap the port.
The venturi port is a small vacuum leak. It's not needed with a HEI + may advance the timing too much.
I found that just enough power fed back thru my GM 12SI alternator exciter (generator light) wire to keep my HEI relay on.
I had to install a diode in the exciter wire so the engine would not run with the key off.
You can use the coil + wire as the signal wire to the relay. This way the relay will be powered while cranking as it gets power cranking from the I terminal on the solenoid.
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