No way would i put in an overdrive w/o at least 3.73 or more gear. Unless you want to be able to go 200 mph...
With the 2004R and 2.56 gears, 4th would be useless below 70mph. But it would be ok at 70+. And the 2.75 first gear would help a lot out of the hole.
The 3.73 would be a fun combination, but I would not go any higher as you'll make the first gear ratio almost useless. Anywhere between 3.23 to 3.73 would be a fun driving combination while still improving fuel economy, and lessening engine wear.
