Thanks for the info. I had guessed that this was the situation from the research that I had done but it's good to have it settled.
I do have the shifters and plan to use them with the 840 and a Regina America 1992 freewheel.
Why did they make the 501 freewheel hub without a freewheel to match?

And if you would scan the tech sheets that would be awesome. I'm trying to consume as much information as possible. I would like to be as helpful as others have been to me.