Steam radiator to forced hot water radiator conversion

dave mark

hello i have some old ornate steam radiators which i would like to use in a separate zone in a hot water system. they have nipples and are connected at the top so can be used for hot water.

could you offer some insights in the best way to pipe old cast iron steam radiators to a new hydronic forced hot water heating system. i would be using some zones with baseboard but wish to have one zone with cast iron radiators in order to preserve the historic character of the house. what is the best way to convert a steam radiator for use as a hot water radiator?
what is the best way to pipe them - single or double? valves needed? best way to tap the old cast iron?
the walls are open and i can do anything needed.