I just ordered the same 2012 F350 4WD Crew Cab SWR and will be pulling a Bighorn 3670....I would love to hear your experiences so far. I just could not bring myself to get the DRW.
We have the same truck (2011 with 20 inch wheels/tires) and would purchase it again. No problems towing anything we have put behind it. Drives like a dream and is very comfortable on long trips. The 3.55 seems to be a good fit. We have a 4.30 in another Ford which is fine for heavy towing. With the 6 speed transmisson the 6.7 never has a problem going up Mountains or long hills. We have also found the braking system works very well letting the computer do the work. Have used the manual feature when going down short steep hills which works well also. You will absolutely love the truck.