Hi John, You have acquired an interesting Stuart boiler that is clearly in great shape.
That boiler will also very nicely power an S-50, 10V, 10H, Stuart Beam, Jensen 20, etc., all with generators or other work load. May also work well with a well built Stuart D10 or Score.
By the way, I still have your twin heater S-50 steam plant with the prototype ball bearing generator.
As for asbestos that came originally in fireboxes, I take them outdoors and treat them with ladies hair spray. Once it sets it prevents the asbestos fibers from flying off in your home or shop.
It is not a perfect solution but it sure makes them safer.
Gil