How to I change the position of the fittings on a cast iron radiator?

I wish to change the position and type of the fittings. The current configuration is bottom,top opposite ends and I want bottom, bottom opposite ends. So I want to remove the top screw/bush and blank it off with the blanking bush from the bottom. I then want to replace both the bushes, one which is round and there seems no way to remove it and the other which is round and has two small protrusions opposite each other. I want to be able to put new valves on it to fit to a 15mm copper system.How to I change the position of the fittings on a cast iron radiator?cast iron rads don't work in the same way as modern ones. the reason the outlet is on the top is so it has to fill with hot water. If you have the inlet and outlet on the bottom the water will just flow straight throughHow to I change the position of the fittings on a cast iron radiator?You should get a plumber as, you could damage the rest of rads heating up. To be honest get all the rads changes to myson, there excellent.