Ahhh, one of my favorites......
"Don't Fear The Gear!"
Rear end gears are just what peace said, they all depend on what you want the car to do. What tranny are we talkin about here? C4? go 3.55 AOD? go 3.73 T5? Go 4.30, and don't look back!
The rear gears will get you in the "azz dyno", FOR SURE! If it's not a drag car, you really won't notice much performance loss, but make sure your head rest is bolted on good!!!!
Generally speaking, you can handle LESS gear (higher number) than you think you can, especially if you have an OD.
All depends on the tranny dude, so fill us in!!!