That isn't much to tow. My wife has a Dodge 1/2 that's rated to tow 13k and it does fine. My son's '15 F150 tows 7500 easy as well.
I'd go with an engine trans combo that's known for reliability. These new turbos look good on paper but time will tell. Turbo's get expensive quick, new engines with popping head bolts, bad gaskets, slipping transmissions, etc. are not what I'm interested in. My choice would be an F150 with the 5.0l first, Second a Toyota Tundra, third would be a fight. I have had to many problems with the Chevy's I've tried, the Dodge has been fine but isn't as comfy. I don't look at Nissan.
New turbos? Ford has had the ecoboost for 10 or 11 model years now. Plenty of history. The numbers look good cause they are.
