So you've found a 460 V8 (good motor but thirsty) with a C6 auto transmission (good tranny). The axle is what they call the "Sterling" and is a heavy duty one commonly used in diesels.
So, what you've got is basically a beast. It would tow any Airstream ever made, probably with a second one hooked to the back of the first one.
It will be thirsty. I had a Mercury Marquis with the 460 V8. I loved that car. But even in super tune, the best it ever got was 13mpg. When the carb was getting worn, I saw 9mpg on the highway and I'm afraid to guess what it got in town.
Pulling a big Airstream, I doubt this truck would get 10mpg. But, you won't run out of power
Best of luck,