I do alot of cross country driving (about 12 trips so far this year that have been longer than 1000 miles). I set the cruise control on 80-85 and let her run. Because of the lower compression ratio of the VG30DETT, I have noticed about 70 miles more cruising to the tankful of gas.
I still have the factory 4.08 rears, and it is actually perfect for everything but long highway runs. 3700 rpms is too high for highway cruising.