go with 4.10's theres some videos on both and how the rev as stickys
Most stock mustangs have 3.27 gears from the factory. I have no idea why Ford put these gears in our cars because they’re awful. Despite what some “experts” might tell you, gears will not decrease your top speed in a mustang; in fact, they’ll probably increase it. If you were to top out your car with 3.27 gears, you’ll notice that the power just stops when you shift to 5th gear. This is because you are not in the car’s power band to pull the car up to higher speeds. Not only will steeper gears allow you to pull quicker, but they’ll also keep you in your power band which will, in turn, enable you to pull stronger in 5th gear; something you could NOT do before. Other experts claim that you will lose gas mileage due to the higher RPMs that your car will now be traveling at on the highway. In reality, you’ll lose maybe 1 MPG at best.
By far, the biggest misconception out there, is that 4.10s are “too much gear” for a car. These people that tell you this are mistaken. Those people are stuck in the pushrod days where the cars can’t rev past 5500 RPMs. Our cars rev to 6000 RPMs for a SOHC and 7000 RPMs for a DOHC. Our torque comes on later than the pushrods, hence the need for the steeper gears. Sure, there are instances where you might want to get a different gear ratio if you have a power adder or are a drag only car, but be it Auto-crosser, Open Tracker, or Drag Racer, do NOT get less than 4.10 gears for a daily driven N/A Mustang.
Your auto will not rev like a stick because of your computer regulated shifts and your overdrive. Your RPMs should be actually lower in top gear than a 5speeds top gear. It shouldn't cut your top speed any. Sometimes you can reach a higher top speed with steeper gears. If anything, it'll get you to top speed quicker. Personally I wouldn't want to see top end, sometimes that has disaster written all over it. If you can't get them in a quarter mile or a little longer, let em go. If caught racing from light to light or a short distance, it'll probably be a fine. Get caught racing top end doing 100+, it's going to be a very sad day.