I already sense the flames but if you have a choice between a Liberty Extreme 4 speed and a 5 speed clutchless, choose the 5 speed. I race in NHRA SuperStock with a Liberty 4 speed clutchless for the last 10 years and can verify that maintenance on a 4 speed is, exponentially, higher than a 5 speed. The problem is universal to any manufacturer's 4 speed clutchless; the gear ratio spacing is simply so wide on a 4 speed, by comparison to 5 speed spacing, that gear rpm equalization damage during the upshifts accelerates to the point that 3rd speed dogs and slider require service (replacement) between 12 to 20 full rpm shifts. This is NOT an issue with the 5 speed boxes, as SuperStock users report that they easily go 100 runs without requiring service. You will hit the B.S. wall when you attempt to verify what I am reporting from mine and several other S/S racer's 4 speed experiences. Don't misunderstand, my Liberty Extreme is a brute and this is the only issue I have ever had with his trans. Additionally, don't miss the fact that a ProStock car is 2350lbs, requiring a lot less 1st gear ratio than a 3300lb SuperStock car which calculates into causing those gear spacing statements made earlier. Choose wisely, good luck.