Migrate customized toolbox items from 2011 to 2013

I wish to migrate the contents of a vendor's 2011 toolbox to my current 2013 toolbox.

A vendor my company is dealing with has modified a number of parts in their toolbox to include custom properties and part numbers, mostly nuts, bolts and washers.

When I open the files containing their machine designs the assembly files ignore the part file copies of the customized components and instead pull in the standard parts from our Solidworks 2013 toolbox, which lack the custom part numbers and properties. This means when we open the assembly drawings, the drawings have blank spaces in the bill of materials in place of the part numbers, etc.

Alternatively, is there a way to get the assembly file to pull the components from the directory containing the modified versions and not from the toolbox?

I have tried using the 'add to library' option, but there are a lot of components and apparently I can't just bulk copy them to the tool box.  They have to be added one at a time.

I have been manually replacing the standard components with the customized components on each assembly, but again there are a lot of parts.  It is inconvenient and creates a possibility for errors.  Besides, this is supposed to be a turnkey operation, and I really don't have time to fix this one piece at a time.

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