didnt read that you had an automatic the first time. google whatever transmission you have and look up the ratio for the gears then you can plug it into the formula below. you can try out a bunch of rear end gears to see what you would like the best.
RPM=[(MPH)(Trans Gear Ratio)(Rear End Ratio)(336)]/(Tire Height in Inches)
I swapped mine from stock to 3.73 Richmond gears and they made me ;D so that's a good idea. I didn't lose hardly any mpg and it gained a respectable amount of acceleration. I'm happy with it. I have an aode automatic trans.. same as you if yours is stock. it runs a couple hundred rpm's higher and the speedo runs 3-5mph faster than what you're really going but other than that it's all good. I've heard 4.10's is another good swap to do with this transmission due to it's broad overdrive band.. hope this helps ya a bit! later! O0