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I think a 3.00:1 or up to a 3.50:1 would be good, if you ran the taller gears like 4.11:1 you would be turning about 4,000 rpm at 70-75 mph. Here's the formula MPH= rpm x (tire radius in inches) divided by (axle ratio x 168). Here's for 3.50 @ 3500RPM: 77.38mph = 3500 x 13 (for a 26" tire) divided by (3.5 x 168). A taller gear is for performance is great for increasing your torque multiplication output, but decreases your gas mileage and increases wear on the engine. Good Luck.
 

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Also if you know your final drive gear ratio, Currie Enterprises website has calculators that will fill in RPM or MPH for you, not that math isnt good for everyone to do to keep sharp.
 

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I cant stand my car in fourth gear going 60 miles an hour. and i have a 2.79 rear. Id probably die if i witnessed 4000 rpm down the highway. i mean thats screaming. Stay with a 3.00 if you are concerned with highway.
 

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My 3.50:1 is too low (High numerically) for extended highway driving in my opinion. A 3.00:1 would be a good highway gear yet still adequate for a little grunt off of the line with your combination. The final drive ratio on a standard old school 4 speed is 1:1. The same holds true for a C4 or C6 auto trans.
 
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