wombat46!

3b's right about the engine and the time frame they were built. My guess is your truck is a 2 1/2 ton as they didn't make 2 tons. My Chev 2 ton is rated around 14500lbs. (don't have access to it but that's what I remember) At 16000lbs makes sense to be a 2 1/2 ton.
This link may be helpful.
Let us know if you pick up that truck!
Cheers, George

http://clubs.hemmings.com/clubsites/chevytalk/index1.html