That looks like a good set up. Like said above max torque on the 6.0 gasser with 4:10 is around 4,000 rpm. Do hesitate to let it Rev when needed on Hills.
I had the same truck and it did well pulling 10,000 lbs.
Steve Rinker
Rochester, NY
2013 Keystone Sydney 340FBH 5th Wheel, 12,280 lbs loaded (scale)
2015.5 GMC Sierra Denali 3500, SRW, Duramax, CC, Payload 3,700 (sticker- not scaled yet)
Take my posts for what they are, opinions based on my own experiences.