Dear Michael,

There is, of course, only one place that comes to mind. Duke has an 
archive of papers of economists (Economists' Papers Project at Duke 
University) and you may want to contact them. I do not know their policy 
on prominent economists who worked outside academia, but they are the 
one obvious place for depositing important papers such as these.

You can get basic contact information at: 
http://library.duke.edu/specialcollections/collections/economists/

Brad Bateman