your S10 is at least a half ton, aka 1000 lb capacity. You will be able to haul the tank, however you may be a bit sluggish, so try not to get in a situation where you have to accelerate quickly.
There is a safety factor involved in rating the trucks, so don't worry about being close to the limit. In my experience, and I'm not so proud of this one, I loaded a 1-ton with 3 tons of material. It was slow and didn't like to turn well, but it's still working fine and the suspension didn't break
