gear ratios and torque

I wouldn't spend the cash on THAT gear change. Not saying i wouldn't change the gear just not the small change your looking at.

First decide at what speed you want to be at what RPM. Think long and hard about what you want the car to do and what you are gonna do with the car.

Run the numbers on the calculator, buy the gears, install gears.

Easy peasy.

For what its worth, most folks seem to go 3.73 for a hot street car car.