ORIGINAL: howarmat

These are the internal gearing numbers for the trannys. Since the auto and manual transmission have different internal gearing, the rpms and such are different in different gears.

Automatic transmission gearing
1st: 3.22 .1
2nd: 2.29 .1
3rd: 1.55 .1
4th: 1.00 .1
5th: 0.71 .1
Rev: 3.07 .1

Manual Transmission gearing
1st: 3.38 :1
2nd: 2.00 :1
3rd: 1.32 :1
4th: 1.00 :1
5th: 0.675 :1
Rev: 3.38 :1

The final drive gear is calculated by using the tranny ratio times the rear end ratio

So in 5th gear you would have
M: 4.10*.675= 2.76
A: 4.10*.71=2.91
A: 3.73*.71=2.64

Ideally a 3.90 gear set in the auto would equal the 4.10s in a manual but they are NOT a FRPP gear so that is one reason most people don't use them.

Notice other gears besides the final gear too......some of those numbers are much different in the auto than the manual. Its really personal preference but usually you are stepping up from 3.31s in the auto and going up to the 3.73s will give you a nice kick in the pants and the RPMs on the highway aren't terribly high this way.

ORIGINAL: Orion_240

since you have to drive 50 miles a day I really would recommend you not get gears but instead put the money into other mods. A tune, CAI, headers, exhaust, etc.

Unless you enjoy spending the extra money on gas for as long as you have those gears in... and taking a roll of the dice that the install will come out fine.
We've had some bad gear installs on MF. Many come with the whine. All will come with higher rpms.
If you had just a weekend fun car I might say try it... But not for a daily driver, IMO