Split the first set with a pilot, to make a 2-6-6-0, and I think you'd have it. I'd personally make it a tender loco, as well. I know the locomen didn't want a tender flopping around downhill. For practical reasons, I don't think a tank would really work in the conditions.
Admittedly, on very basic math (assuming a Standard 12 boiler from a King, and the same number of cylinders split onto both drive sets,) the suggested artic would be around 15 tons/axle