I started out years ago towing our 7,000 lb trailer with my old chevy 2500 with the 350. I tow mostly in the Sierra and Rocky Mts. I hated the way I had to slow down to 45 mph going up the grades. So ...
You might check out the 5 Star tuner for the V-10. Really helped my 14K lb. class C. Climbs much better at lower RPM plus I get a coupe of MPG better on the flats. I wouldn't leave home without it.