As BuckBarker posted, reliability is the weak link here. But, you are not liable if you sell a used vehicle since the purchaser would have to prove the engine was a "known defect", like it had been in a major accident and repaired. It may break down and require frequent repair/maintenance, but that is not a legal defect. The buyer is required to use "due diligence" and assumes the risk of future repair costs when he/she buys a used vehicle. You would be liable if you misrepresented the truck, like total miles. Even if you had been told the truck needed a certain repair, you are selling the truck "as is" and are not required to disclose the recommended repair to the purchaser.
Consumer's Union rated both the Chevrolet and the Fords pretty much equally in reliability, with Dodge third on the list. Personally, I'd consider all three if you found one with the options you want at a reasonable price.