With a 6spd manual, your car either has the performance 3.42 or the 3.23 gears. If the car has the 3.42, then it probably has an oil cooler and the 160 mph speedo, but this is not always the case. It could have the 160 speedo and the 3.42 but without the oil cooler. You'll have to check the option number on the placard within the glove box to make sure which gear ratio the car has and physically look for the oil cooler lines leading from the oil filter mount to the radiator.
Changing the gear ratio to a numerically higher ratio increases the torque multiplication. Lowering the numerical ratio has the opposite effect. When accelerating in the 1/4 mile, a lower gear ratio typically helps with the ET, but may or may not help with top end speed. When choosing a higher numerical gear ratio, it should be chosen and compared to what will be the engine's top rpm at the end of the 1/4 mile, what do you want it to be in relation to the engine's power band, what is the power of the engine and where does it make the power.
Here's a website that can help you with those calculations:
http://www.f-body.org/gears/Or, you just want some low gears (higher numerical valvue) so that your car can trounce just about anything at the stop light grand prix. Most owners on this website say that 4.10 gears for the 6 spd and 3.70 gears for the automatic work really well.