Don't know where you're at, but in about 18 years of owning diesels neither me or my dad have had a gelling issue in any of the trucks we've had over the years. There's plenty of additives in winter blend fuel. I throw the motorcraft anti-gell in if its 20 or below just for peace of mind. Only cold related issue so far was a ruptured oil filter in the duramax when it was about 10 below 0 five or six years ago. As with any winter vehicle you're going to work, don't beat on it until its warmed up and they'll love you back.
As far as turning radius, get a truck/blade combo that will suit your jobs best. For me its a 450 extended cab with a easterner dump with a 9' straight fisher, because I spend 85% of my plow time pushing on the highway. For my buddy, its 350 extended cab short bed SRW with a 8' straight for driveways and small lots. And my uncle had until a few months ago a 250 reg cab/long bed with a 8.5' v boss... he swore by that truck.