If I was looking at getting a used truck to pull your trailer I would be looking at a one ton SRW. I would choose a 2011 or newer Ford; a '13 or newer Ram or almost anything newer than '06 from GM; and I would buy a diesel. Personally I would choose a 2015 Ford with the 3.31 rear end. I would probably put more weight on the overall appearance of the truck than the mileage, although I would buy a truck with no more than 100k miles on it.