I got an Ultragauge last week and quickly realized the answer to my question. I'll go ahead and answer it for others that may be searching
. Basically, there is no magical rev range. The key is to have a steady and light foot. I would try and keep the throttle at 20%TPS and that would allow me to glide between 55mph and 70mph depending on incline/decline. Having 20%TPS at 2500rpm used a lot less fuel than 30%TPS at 1500rpm. Anything below 1500rpm would cause a bog and would use even more fuel.
So basically, the moral of the story is don't worry so much about the revs and more on the throttle. On my last mostly highway trip I averaged 36.2mpg (confirmed with actual miles/actual gallons, not just Ultragauge) cruising between 55 and 70mph and minor city driving. I could have done better if I drove a bit slower, but I felt that I had compromised my speed enough. My next long trip to Toronto I'll try to have some aero mods to see if I can cut through the air a bit easier.
I'm planning on:
blocking the bumper/grill
removing antenna
taping rim voids flush
Removing the spoiler and replacing it with a Bonneville style.