Kevin, when buying used, unless you're looking for "certified used" (only a year or two old) then I would look at buying from private party and just look at/for those trucks that's been well maintained (they kept records). For instance, Ford came out with the 6.7 diesel in 2011. A good motor and tranny that's still being used in the 2018 models.
Dodge has a motor that's proven however, their transmissions have a history of issues.
The GM product (Chevy/GMC) do not have the load ratings that the Ford and Dodge have.....or at least I've read that on the RV forums.

Not sure where you're located but if you're close to a large metropolitan area, go on line to Auto Trader and/or Truck Trader. Sooner or later you'll find what you're looking for. Then you can get a better suited toy hauler.
