Lower RPMs does not mean better gas mileage. More RPM's is better than less, especially with the 3.0L.
4.88's BARE minimum for a 3.0L and 35's. I'd even go 5.13's, but if you are still going to do more highway than offroading, then you can get away with 4.88's.
4.56's won't cut it bro.
See this down at the bottom of the page: