F-150, 3.5 non eco boost, 355 rear end

I had one for a work truck. For short trips, its fine. It gets up and goes with no problem. It's just revving like a rally car to do it. But it made quick work of both long 7% climbs and much steeper on-ramps.

Beware the frontal area will be the bigger factor in how much time it spends in lower gears.

the 3.5 will rev a fair bit as it makes its torque in the higher RPM band, however the rest of the truck is still up to task. I wouldn't worry about anything 4000lbs or less ready to camp.

Popups, maybe some of the smaller single axle ultra-lites. With that size of truck, and that engine it is not just weight by frontal area that will be an issue.

Look around the campgrounds at what people are towing in with midsize SUVs, and that about where you are at. They typically have the same 3.5 NA class engines, but in a lighter package. Lighter package, advantage SUV, heavier suspension, advantage truck, probably a wash between the two.