With a debt of gratitude to the insights from this forum - and
@Markarian421 in particular for putting together his spreadsheet - I finally settled on 275/70/18 KO2s mounted on Method 316s with +18mm offset in Titanium Grey. I did the spare too, and as you can see from the rear photo, it fits, but droops about 1-2” below stock. Can’t wait to get them off-road and get them dirty.
So far, after about 500 miles, I’m averaging about 18.7 mpg (about 20.7 on a recent road trip). Ride with the E-rated tires is only noticeably stiffer over potholes at speed. Road noise was noticeable if you were listening for it above 70mph, but not intrusive.