Bill,
You seem to be the person to ask.
I have restored a recirculating heater for my 1950. The cable shut off you had shown installed on the input hose, does it shut the flow of water off to the engine as well as the heater if used? Or are the hoses specifically for the heater use? If is just for heater and can be shut off, where did you find that aftermarket cable shut off part? Right now I have one hose connected to both hose http://good-times.webshots.com/photo/2090509180103567918wZeziKoutlets, see pic

Eric