Well I think we found the Ford haters! The 6.7 is actually a pretty good engine with little statistical trouble. Hard to find posts about "no trouble" because those folks don't post. So, here is one: 2012 F-350 CCSB SRW 6.7 with no trouble other than the waste gate vacuum noise fixed under warranty even though it was not an operational issue. In Ford land as stated, little difference between 250 and 350 other than aux spring, spacer, VIN ratings, and the 350 emblem. A SRW truck will haul the trailer the OP talks about, but dually guys will jump on soon talking about stability which a dually will certainly add. Suggest 2012 Ford or later because of some transmission troubles with the 2011. Almost shocked that a bunch of folks haven't jumped on the infamous Ford high pressure fuel pump issues. Funny thing if you run water, ethanol, or gasoline through the high pressure pump it blows, and that's Ford's fault. OP should buy the truck he likes the best--if Ford was initially last, leave it last despite their good documentation.