The specs look close to my trailer which I tow with my 5.0 3.73. It tows it well power wise. The transmission having 6 gears helps a lot. I lock out 6the gear and cruise at 63mph in 5th at 2000-2100 rpm or so and average 10-10.5 mpg so far after 1,000 towing miles. The trans will drop to 4th for medium hills and 3rd for big hills but the engine is not really screaming and will easily accelerate up 6-7% hills in 3rd at 60mph. I haven't had it over any big passes yet but live in a fairly hilly region and don't foresee any power issues with this setup even in the mountains. No doubt the Eco would have more torque, but I think the 5.0 will pull it fine. I haven't driven a 3.55 rear truck to compare, but I would error on the 3.73 side.
Where I'm not as in love is the trucks stability. I've gotten it dialed in pretty well now, but I did get blown around by wind more than I preferred before I tightened my hitch a bit. The stock p tries, soft suspension allowed more movement than I preferred. If you haven't bought the truck yet, I HIGHLY recommend holding out for an hd payload equipped model.