Did you consider changing the gearing to compensate the larger tires ?
It's not really possible with the locked computers on the Mercedes. But I honestly never felt the need to. When it was on stock tires, it would wind out so bad on the fwy at 70-80 mph. With the 35s, it would cruise at 2200 RPM or so. It would return a consistent 15-17mpg even on the chunky mud terrains.
A real low range t-case with 2.7:1 was the one upgrade I would have liked. I would not have changed the axle gearing even if I could. Van is sold now and onto a new set of adventures with the new owner.