I always wondered if anyone ever adopted a manual transmission to a 6.9. I'm betting that the 3-speed automatic probably holds the car back from a performance/efficiency perspective. Redline is 5,000 RPM, right? I think that is probably the limiting factor in top speed on this model, as aero is decent and the torque/horsepower is certainly there. I'll bet that a 6.9 with a 2.65 rear and a 5 or 6-speed manual, with overdrive in the upper two gears, would be an honest 150 MPH car.