The mount that I have for my 727 has no rubber on it at all. Is this normal or is my mount incomplete. It is the shape of W.

I would have to believe that even a slush box needs some kind of a vibration damper or flex in the mount.

I need to know so I can build my skid plate.

There should be a w shaped bracket that bolts to the trany on one side and the other is bolted to a piece of channel iron. Between the that piece channel and the cross member (xcase skid plate) should be your rubber mount.
Hope that helps.