Any gas motor over 350 cubic inches can probably do just fine. Put personally id want it to be f350 or a 3500 if you are doing any bagging. If you just let it fly and do not collect anything than a f250 or 2500 pick up would do but id never want that kind of mass on the brakes of a smaller truck. Yes I know it has trailer brakes but the truck brakes still get a work out.
That said once you go diesel there is no going back. I can remember a break down once where my trucks fuel pump went and I coasted to a side street and managed to pull in but I was still partly blocking the intersection. And I was now on a beginning of a hill so I couldn't just unhook the trailer I needed to be on flat ground first. I had ram 1500 quad cab long bed maxed out with grass the pile was higher than the roof of the truck. The trailer was 16 ft with 2 ztrs on it one with a collection system then 2 back packs 2 trimmers and all the extra gas. Easily weighed 12-13000 pounds my only available truck was my 89 gmc 3500 diesel 6.2 but it had 3 yards of top soil in her for another job. That truck pulled herself the Ram and the trailer and the mowers up this steep hill like nothing it never even went above idle. How many gas trucks you know that would move 18,000 pounds not including themselves with that kind of ease. As I said once you go diesel you will never go back.