Good estimate on their chart… guessing how much you’d weight. 
As I recall, my 1/2 ton says 1350 pounds cargo. That leaves about 600 lbs… really big driver/passenger. Oh, I forgot the pygmy seats in back, plus the dog.
Good info, thanks again. Sounds like I should be good to 800 lbs cargo without much worry, keeping on the safe side of the limit for a 46 year old truck.