Keisler Tremec TKO 600 5 speed

I've got a TKO600 behind a 500 c.i. 440 and regularly run it up to 6000 rpm with no issues with shifting. I've had it for several years now. I think you'll be fine especially since you've dynoed your engine and know exactly when it's making peak hp. I too am running a 3.91 gear. With a 28 inch rear tire and the high first gear of the TKO it's like running a 4.23 gear with the old four speed. Be sure to run a tall enough tire and you should be fine. You're going to like that combo. :burnout: