I put 3.73's in my old 95 3.8 Auto & the speed limiter held it to maxing out at 85mph... lol for a 3.8 it really wanted to move but the rpm's were to too high for my taste on the highway... 85mph was a little over 4,000rpms with the AOD.
4.10 for Auto..thats what i have and man it makes a huge difference. You will feel it when you step on it but make sure you have positrack. Also upgrade to a 8.8 rear end.