[elhigh]

Consider a trailer tail of sorts for your back end, belly pan and skirts.

The tall rear end helps a lot, keeps the revs down.

I used to drive a 15-pass van for work, approx the same age and never beat 15mpg, but I was exclusively doing city traffic. New brake pads every year and every year had to explain to the boss why I needed them: "Because I cover 25,000 city miles every year, Stan." If you're going to be mostly highway I think you can do it.