Condition of your electrical/charging system may effect how well the HEI functions. Twisting brown and blue together will send system voltage to the HEI but, Is that 12+ volts at all times? If idling in gear causes your amp gauge to move to discharge, headlights dim, etc.., Or maybe your 67 doesn't "currently" have this condition.
In any case, A more direct power supply to the HEI module and e-coil via a relay can only help.
The brown and blue, your ignition switch, everything in the path is/was barely adequate for its original duty.
