One thing to remember.
When you raise the shift RPM on a sled you are effectively increasing its top speed capability as well.
For ex:
Stock
23/38 = 1.65:1 ratio
Stock shift RPM = 8500
at a shift ratio of 1:1, with 9 tooth drivers the sled is capable of approx 110mph
Piped/Mod setup
23/38 = 1.65:1 ratio
Mod shift RPM 9000[ 6% increase over stock]
at a shift ratio of 1:1 with 9 tooth drivers the sled is capable of approx 117mph[6 % increase]
As you can see raising the RPM by 6% is just like increasing the gearing by 6%
JM.02c
Bob