I made some updates to support our store, new version with these updates has been submitted.
This new version was only tested on Zen Cart 1.5.1.

Updated the files to resolve bugs and to add an ability for showing option values as out of stock on product page, attribute qty on product page, and stock of products without attributes in cart. All setting are controlled by options in the admin under Configuration/Stock. Details of changes are included in the package in the file Updates.txt.

Remember to always test prior to using on your production site.