Jim,
My buddy has the 6speed in his Viper and we just put the TKO 600 5 speed in the CooX Lister. The 5 speed with the 3.42 diff ratio gears and the .82 overdrive (Vette Drivetrain) is perfect. In comparison, behind a higher horsepower old scool car like a Cobra, I prefer the 5speed over the 6 speed, and think you would too with that monster motor...
