Towing with a 2009 Ford F350 6.8 V10 4.10 Supercap LB

You do NOT need to change from your 4.10, especially with a 4X4. In hilly terrain I would lock it out of OD and use the tow/haul making your 4.10 into a 4.56. In the days of three speed trannies axle ratios were very important but not with a five speed/OD tranny. I agree a 3.73 behind a gas engine is too tall a gear for towing, but not if you had a diesel.