dumb question

Basically with lower gears your car is going to wined (rev) up faster. If you had 3.27's (common stock) and you upgrade to 4.10's then that is almost one complete ratio higher. The engine is going to turn the same but it will spin the tires faster. To answer your question you are going to get to 40mph (or whatever speed) faster with 4.10's than stock gears. However you will lose some top end speed. Remember you rear-end can only turn so fast.

you will be quicker from a roll with 4.10's as long as you can shift fast. Most people have problems launching with 4.10's