You might gain 1-1.5mpg with those suggested changes. But you'd miss the features.

 

Just returned from a trip to the east coast with my van, an '06 E250 with the 4.6 and 4.10 gears, and 245/75R16s, otherwise the van is all stock and we travelled essentially unloaded with only a couple hundred pounds of cargo. Total distance covered was about 3000kms, half of that was essentially flat and the other half was hilly. On average the truck returned 16mpg US, 17mpg on the flats and 15 on the hills, in both cases I had the cruise set at 110kph which according to the GPS was more like 107-108kph.