Unless you plan tow over 5K lbs behind your truck while you carry the TC, I would suggest getting a gasoline powered engine. In the end, you need to buy a diesel if you need something requiring that capacity because there really is no cost saving once you pencil out acquisition and maintenance costs plus it takes away from your payload.
Now if you decide to tow an enclosed trailer (like I have) behind you, definitely shop for a diesel because the driving experience will be so much better and you can enjoy the journey as much as the destination.