I drive a manual and I'm torn between 3:27s and 3:55s. You didn't mention if you have a stall converter in or not.
My suggestion would be to get your car dynoed and see where peak HP and Torque are made with the combo that you intend to use. Base your gear decision on which ratio will put you and keep you in the best part of your power band for the longest. With a Kenne Bell, you torque and HP curves will pretty much mirror your N/A curves only they'll be considerably higher on the scale.
3:73s I think, are going to be too steep for the amount of torque you'll be putting down very low in your RPM range. Having never driven a KB powered AOD, I can only guestimate.
A low stall converter and set of 3:27s would be badass on an otherwise stock combo with E7s though. If you weren't in a position where you had to do it now, I'd say to keep your 2:73s and try it out before swapping to a steeper gear.
I'm looking at some stock motor dynos and the crossover points for Tq and HP are between 4000 and 4500 with a huge amount of torque starting at 2300 and carrying all the way thorugh 4000. Have somone better versed in AODs take a look at that information and see if my assessment makes sense.
I'm thinking 3000 stall and 3:27s will keep you riding the torque curve well in to the transition where the HP takes over at about 4500 RPM.
It'll be up to you to figure out out how to keep all that torque on the ground. LOL
