TAD, please know that I have an '04, 5.3 liter SSR. The performance difference between mine and your 6.0 is noticeable. I would think a 4:10 gear, plus a tune, in your 6.0 would break things loose all day long. As for rpm, add 300 to 400 rpm at 75mph.Thank you 4:10 was what I was thinking, you know it to break them loose on dry pavement? And do you know approx RPM cruising 70 mph?