so with your 4.7, for example, 60 mph in 5th gear iirc should put you in the 2950-3000 rpm range. for a rough estimate, since i don't have the chart i made and don't feel like doing the math right now, you can assume that the tsx 6th and the 4.3 fd will each bring your rpm down, at the same 60 mph, 300rpm. combined they will put you at a 60 mph crusing rpm of about 2400. the tsx 6th obviously only affects the previously non existent 2nd overdrive spot, where the fd affects all gears. swapping to the 4.3 will make it take longer to wind it all the way out to redline, it'll feel a little slower without an increase in torque on the part of you engine. for a daily driven car that sees alot of highway time, i'd go with both. if it's short track times (like autox) you're more worried about the leave the 4.7 fd in and just go with the 6th gear mod.
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