I used to tow a 2011 27' FC with a Suburban 1500
. All the vehicle ratings and trailer specs were fine; I was within all the limits, although at the upper end of my TV's tow capacity. Everything worked fine, towed over mountains and across the country. The only problem was that I was always managing the engine in any but the smoothest terrain. And many times that made towing a pain, stressful.
Looked around for a couple years, talked with a LOT of AS owners and finally settled on overkill. Just bought a 2015 Chevy 2500 diesel. I wouldn't have believed it if I hadn't experienced it. Towing now is such a breeze, the trips are relaxing.
I'd recommend you look at a TV where the weight of your AS is not at the upper range of its capacity. I passed on the small block diesels simply because of that. With only 2k miles on the odo so far, mileage is still settling in; but I find, traffic permitting, that I can set the auto pilot and leave it in in virtually any terrain. When on level, I'm cruising at 1500
to 1700 RPM, and grade sometimes causes a downshift to 2000+, but nothing like what I had to do with my Sub.