Fusion 3 seems only to support snow leopard server, not snow leopard?
Why would you run Snow Leopard in Fusion 3? You either can run Fusion or you cannot. If you cannot then even in emulation it makes no sense, does it? Also this would circumvent Apple's ROM in the code ... maybe down the road it would be supported on newer OS X 10.7.xx or higher but natively in Snow Leopard or lower just doesn't make sense.
If all you want is a "sandbox" to play around in, wouldn't a better approach be to simply clone your system to an external drive and then boot from that?Sometimes it's nice to have a virtual SL to test things out on. It does seem to go against the EULA, though.
It can be fairly easily done but I'm not sure that it is within the rules of the forum to tell you how. Luckily Google exists.