A 3.07 (which I have in stock) is an excellent diff swap for a 240D. I have personally swapped this into a couple of customer 240D's. I believe Uncle Kent Bergsma has a video of him doing this diff swap on youtube and you can actually see the acceleration.

It will be slightly slower on the takeoff, but the 240D is already one of the slowest vehicles on the road, so a second or two off acceleration is not too noticeable.

The benefit of this swap is that freeway/highway cruising RPMS will be lower and the car will be considerably quieter/tolerable at 70 mph than with the 3.69 differential