I'll assume since you made no mention of it, your car is basically stock....in which case I probably wouldn't consider anything lower than a 3.73 ratio. Remember, your engine isn't making any more power, any higher in the power band, so you'll be through it before you know it. Zipping through the power band in a hurry sounds like a positive thing, until you realize you're also zipping through your torque curve. You aren't allowing the lower RPM torque that the 5.0L OHV is known for to do it's job and thus aren't going to experience the seat of the pants feel we all so desire.
If you had better heads, cam, intake, etc and added 500-1000RPM to your power band, then you would fair better, but as it sits, I'd either consider going with a little less gear, or adding a better top end.
That being said, I wouldn't bother with the gears at all without paying an equal amount of attention to the stock AOD. In factory trim, that trans is a slow shifting "slushbox" at best. The addition of a good shift kit (TransGo, B&M, etc) and heavy duty plate style transmission cooler installed at the same time the gears are should be mandatory. And if funds allow, a little looser converter will liven the car up from a dig as well.
Better start saving.