The absolute smallest clutch gear that will fit and the absolute largest axle gear that will fit, and wide open throttle, will give you the most power strokes per lap. I don’t think that will have any benefit though. You’ll just be red lining all the way around the track.
One aspect to going faster, turn more RPM in the same amount of time. I.e. you turn 3600 – 5000 and I turne 3600 – 6000. I can run a lower gear ratio, I can out accelerate you and be going just as fast at the end of the straight. Maybe faster. This is an oversimplification but it's a simple problem.