Removing a large inlet pipe from a cast iron radiator

[lswee]

I have recently purchase a couple of cast iron radiators from a local reclaimation yard and I am planning to install these in an old cottage that I am renovating.

The problem is that each of the radiators have a large (1 1/2 inch) inlet/outlet pipes which I need to remove to put in a blanking plug and reducing bushes to ensure that the radiator will fit the new valves. The inlet/outlet pipes seem to screw straight into the radiator (i.e. no bushes or joints) and inside the pipe there are two raised ridges which are opposite each other.

I'm sure that there must be a tool which slides into the pipe, into the raised ridges (i assume its round with two corresponding notches cut out) to allow you to unscrew the pipe.

I cannot find a tool like this anywhere does anyone out there know what this tool is and where i can get one?

[onedayimightwin]

was really hoping to see an answer to this... I realise this is a year on. But did you manage to sort this out? I am in exactly the same situation and am wondering what the tool is. Did you just remove the entire bush in the end. I really hope you get this message or that someone else can answer.
Many thanks