Tim, I doubt it.
The 160/5.6 Pro Raptar is a 6/4 plasmat type, a Symmar competitor. Some, including the dread Dagor77, insist it is the best of the 6" or so f/5.6 plasmats. I'm not convinced of this, especially since I don't have any of the others and since Andrew's descriptions of his wares are a little, um, extravagant. But mine is certainly a good lens. AFAIK they were all sold in a blue-faced Rapax, I'm not sure what size so don't know if the cells will go in a Pi-Alphax.
I believe that the cells Surplus Shed sold were for a tessar type lens, and an undistinguished one at that. Check to make sure that they're f/5.6, as you think, and count reflections too. I betcha they're 162/4.5.
Cheers,
Dan