Buying a 39' Keystone Alpine 3660 and picking up Oct. 1st.

Go with the 350/3500. If buying new, there isn't much of a cost difference. Is that the published unloaded(dry) weight(usually a ficticious number), or the GVWR(much better planning number)? I ask because you are getting close to the single rear wheel vs the dual rear wheel decision point. I happen to tow my Cardinal in my sig with a 1-ton SRW, and am within towing specs. My cardinal weighs in at 15K ready to camp, and I wouldn't go any heavier of a trailer unless I went DRW truck too.