Hopefully some of the engine guys will chime in for some better advise.... But here is my
In my experience the best way to determine if it will help or not is to try it both ways and see which way best suites your needs. Be sure to fine tune the engine in both configurations (timing, carb settings, etc.) and drive the car under YOUR normal conditions..... then you decide which is best. The spacer will most likely just change the location of your power band. Giving you more HP/torque at a different RPM range.