I also recommend the U1300L. With midrange axle/diff ratio (5.3:1, but down to 4.5 is possible) and overdrive, with OM366A turbo, cruising speed can be as high as 70 without exceeding 'pink' line at 2400 (redline is 2800).
But, IMHO, that's too fast for sustained speed. I prefer about 60...