/6 with 4 Speed OD, rear gear recommendations?

I have a similar setup in my /6, and I'm planning to switch to a 3.23 ratio. Like you, I'm not a tire-screecher, and am looking to retain the awesome MPG I'm getting with the 4-speed OD and stock rear gears(2.76?). Most people like the 3.55 and up, but they might be more concerned about launch speed.

Awesome MPG is what I am looking for. This car is for cruising and enjoying on a regular basis. If I want speed, I have access to a car for that. Funny thing is, the "fast" car has been out 3x this year, and I have driven the Dart 3x in a week.