The Chevy site says this concerning the C4500 GVWR & GCWR:
GVWR: 16,500-lbs. (standard on 2WD Regular Cab and Crew Cab, Motor Home and Commercial Cutaway models)
GVWR: 17,500-lbs. (standard on 4x4 models)
GVWR: 15,000-lbs. (optional on Regular Cab, Crew Cab and Commercial Cutaway models)
GVWR: 16,000-lbs. (optional on Commercial Cutaway and 2WD Regular Cab models) (1)
GVWR: 17,500-lbs. (optional on 2WD Regular Cab and Crew Cab models, Motor Home and Commercial Cutaway models)
GCWR: 26,000 lbs
GCWR: 30,000 lbs with available Allison 2350 Series transmission on 4x2 models.
In the real world (day in day out where trucks really live) I've found the one tons C30/F350 will haul 3 tons & the F450 will haul 4 tons. Add a trailer with 4 tons of payload and you will have all you want. And please I don't claim to know it all but I have made my living around trucks for 40 years.
I didn't check the specs on the 5500 but I would guess a 5-6 ton payload would be about right. I've drove and repaired class 7 trucks and 8 to 10 tons was all they wanted in the on/off road hauling we did.