I think this would be a great choice. The 37s will be a much bigger upgrade in Washington than in Moab. Ground clearance isn't the biggest issue on the vast majority of trails. Maximize your value in the tires you have...
What kind of RPM were your turning on the highway going to California? The the tire diameter should be under 7% different so at 3,000 it should only be a couple hundred RPM difference. Is that enough to get you out of the powerband or really impact your fuel economy? I know some engines are more picky that others.
I'm not sure my nearly stock gearing is really the best combo with my midrange cam...it doesn't seem to pull at higher RPM like my 85 did.
RPM range is around 3600-3800 RPM from 70-80 MPH.
