Well, yourself and the group almost had you in a diesel Dooley now! I've heard at least 1 reccomendation in the "3500" category already....lol.
So the first responses were right, this gets asked every day and 2x on Sunday's.
Here's another response. If you were familiar with and/or good at towing, you wouldn't be asking a group of total strangers opinions. So with that in mind unless you're confident in your abilities, buy the biggest overkill truck you can afford for the camper. You will have the most factor of safety padded into the equation you possibly can. And it is also somehow more soothing to tow with a truck that is putting forth little effort.
That said, you don't "need" anything bigger than what you already have, which if it has the 5.7 and is pretty much still like new with those low of miles, it'll tow a 7000lb trailer all over the place, just not with the prowess of a shiny new HD Turbo Diesel.
So which is better prowess, or free? You can always buy prowess later if you don't like free.....