2600-2700rpm @80mph is pretty close.
If you are hoping to gain major economy with gearing, you are setting yourself up for some dissapointment...
Mileage will change very little with any of the mentioned diesel transmissions, they are all within 10% overall. It still takes exactly the same amount of energy to propel a car down the road regardless of the gear ratio. The best you can hope to save is the amount of extra friction or loss of volumetric efficiency caused by the higher rpm. The added friction from 200-300rpm is probably negligable. I have tried driving in 4th gear and the MFA shows very little increase in consumption.
My current "lifetime" average is 6.0l/100km or 39.2mpg(US), mostly secondary roads (60mph) and ~25% city. I am having a hard time keeping my foot out of it, it is a very fun car to drive... I'm quite sure economy could be better if I drove it like a sane person, but it still doubles the mileage of my previous mazda 6 3.0 driven under the same conditions and has more power to boot. I am overjoyed!
I don't think I would stress out about finding the ultimate tall gearset, everything that exists has been mentioned here, there are no taller final or 5th gears than the .68 and 3.44. Just get a 5 speed in the thing you'll love it. I find the engine happier at higher revs anyway. Seems to love running about 2500, much smoother and quieter than 2000.