Looks like an early model cassette, not freewheel. You need 2 chain whips. 1 to unscrew the smallest cog. the other to stop the cassette from turning.
You can probably find some combination of hollow axle & cones that will work. See if your LBS has the parts. Might take a bit of trial & error to get the right ones.
Last edited by Homebrew01; 04-10-12 at 11:30 AM.