331 is the magic answer it was fords way to try and boost the millage to drop the guzzler tax. it didnt work.
Most guys run 3.73 as the car has enough power to pull through with that ratio.
I am in the high 11's with the stock 3.31 so anything is possible. I also like that my top speed is not effected as the car will haul ass. I have had it around 150 and it still had all of 6th gear to go.