If you're looking to convert a blind magazine Super Shadow to a hinged floorplate Ultimate Shadow format, I think that you are probably SOL. I tried to buy the 1-piece bottom metal before USRA went under and they wanted $150 for it, so I opted out. You might find the part(s) or some better directions toward the part(s) over on
www.wssmzone.com. If you do find a source, let me know, 'cause I've got 3 Super Shadows that I'd consider converting to the Ultimate Shadow format.
Good luck!
Jeff