yea, if you were m6 i would go 4.10, but probably 3.90, or 3.73 is your best bet for the stalled auto. I would highly suggest the genuine gm gear over all otheres. It is made by AAM, and you can get the motive master install kit. The gm gear costs like 20 bucks more then motive, but fits great, i have no whine at all, and is very strong. You can get the gear with the install kit from Speedinc. Thes best thing about the gm gear, is most of the time you dont need to shim it at all. The tolearance is perfect for everyone i have done, which is amazing to me, because even the motive gear needs to be shimmed a little.
If you dont mind the higher rpms, or gas mileage go with a 3.90....
Chris