One thing to remember though,
when you do loose it (Wet moreso than dry) with LSD, YOU LOOSE IT BIG TIME !!!!!
At least without LSD, you only spin 1 tyre, and the car is somewhat stable. (I.E. no forward motion, no rear end trying to overtake the front).
With LSD, when you loose traction, the back wants to overtake the front and step out, which is very very fun when you have some control, but very scary when you are least expecting it.:oo1:
If you are going for a diff off a different model, (I.E. wreckers) then just be sure that the ratio is the same, otherwise your speedo will be out of calibration.
I think with EA Multi Point Injection 3.9 Auto (I am assuming this), the fitted ratio is 3.08, so you will need to get the same ratio as this in order to have the same speedo readings.
The Ratio should be on a metal tag on the diff.
Just a little note.
A higher Diff ratio (E.G. 3.23 or 3.45) will yeild better acceleration, in place of a higher top speed, (Auto gears will change earlier as well) A higher ratio tends to use more fuel on Highway cruises, as the engine is reving higher for a given speed.
A Lower Diff Ratio means that acceleration is poor, but the car is capable (If the engine is powerful enuf) of a higher top speed.
A lower ratio tends to be less thirsty on the fuel, due to lower Engine RPM needed for Highway cruising.
Hope this helps