I figured out how to move radiators around. I found a couple of wheeled platforms from Harbor Freight that were reduced as a special for Inside Track club members. They are designed for moving cars, and a pair of them are rated at 1500lb (I forget if that's 1500lb per platform or per pair, it doesn't matter for my purposes). They are also pretty low to the ground, so I could lift one end of the radiator while my wife slid the platform under the legs, then put the brakes on the platform so it wouldn't roll while I lifted the other end.
The wheels are obviously heavy duty but the only mark they made on the floor was a very slight groove as they rolled. So now two radiators are sitting in the room I've mostly finished, and I can get at the floor in my latest work room. So now comes a lot of time on my knees, sanding and lacquering the floor. I'm not looking forward to the lacquering part, usually I'd open a window and use a fan to vent the fumes outside but when it's below 20 degrees outside I don't plan on leaving a window open all day. I guess we'll just have to deal with the fumes, although it's a low VOC lacquer so they aren't as bad as the fast-drying stuff.
I still haven't figured out how to drag a 200lb lump of iron up the stairs, although at least now I know how to move it once it is upstairs.