It's a tad more tricky on a freewheel, as they are more resistant to disassembly than cassettes.
Also, the inner diameter of the f/w sprockets are different - not only when compared to a cassette, but also between inner and outer sprockets. And I've never seen a spacer kit for f/w for sale. You'll probably either have to make them, or scrounge a few scrapped f/w for parts. And even then you won't be able to use any sprocket in any position.
Last edited by dabac; 10-10-11 at 07:10 AM.
Reason: spelling