I don't think that is necessary. If you modify something that changes the power band of your engine then you will have to change the shift points. For instance, if you upgrade your cams and intake then you will have to shift at a higher RPM because the engine will make more power at a higher RPM than it did before. If your car stopped making power at lets say 5,800 rpm stock and you upgraded to a cam and intake with a 2,200-6,200 rpm range, then you can change the shift point to 6,200 because now you will be making power up to 6,200 instead of dropping off at 5,800. Changing to a numerically higher rear end ratio does not affect where the engine makes its power so you can still shift at the same rpm as before. The numerically higher gears just gets you into your power band quicker. If anything, you will lose top speed because at any given speed you will be at a higher rpm. So for example, if you were going 150 mph in top gear at 5,800 where you power drops off, a numerically higher ratio will have you at 5,800 rpm at a lower speed but your power will still drop off just the same...it's always good to experiment tho as long as you're careful not to damage your car...