Commenting on the first youtube video, I was under the impression that a diesel could pull any grade at speed in OD pulling their max weight, at least thats what I have read on here. Sorry I had to say it, I'm done being sarcastic.
I used to drive a 99 E-250 with the 5.4l for work, I wasn't happy with the performance pulling a 16' enclcosed trailer with 2000 lbs of equipment in it, downshifting into 2nd at every overpass or into a headwind. Granted this was one of the two valve engines and I have no idea what the rear end ratio was. I must say that that engine was one tough mother though, we use to say to just floor it and forget it when driving that van.