I guess nobody else has any suggestions either.

I did the following:

• Aperture > Preferences > Appearance > Browser Brightness = 100% White
• Click on “Library Photos”
• Grid View
• Command-A to select all photos in the library
• Aperture > Stacks > Open All Stacks
• Adjust grid size to minimum, enabling me to see as many thumbnails as possible
• Slowly scrolled through the library, easily seeing the dark gray stacks against the white background
• Selected all items in stacks (click on first image, Shift-Click on last image
• Applied the keyword “Stack Item” (hot keyed to #1 key)
• Repeat above 3 steps until all stack have keywords 
• Created a smart album for all photos with the keyword “stack item”
• Command-A to select all photos with the keyword
• Aperture > Stacks > Close All Stacks
• Command-A to select all closed stacks
• Applied the keyword “Stack Pick”( hot keyed to #2 key)

Now with all stack items having the keyword “Stack Item” and the stack pick of each stack also having the keyword “stack pick”… it will be trivial to recreate my stacks after I migrate to LR

Using my smart album,  I checked each of my stacks to be sure that all of the items had the proper keywords.   As expected, some albums only had the stack pick with keywords applied… because I must have applied keywords to a closed stack.   I fixed the rest of the stack elements so that all have the proper keywords.

It was easier than I suspected it to be.

I hope this helps someone migrating their library to a new program.   I am personally moving to Lightroom.

/Jim