How to force "import from another catalog" to import pictures already in the destination catalog?

I am trying to import catalog A into catalog B, my main catalog, which is huge, but the process is omitting some of the images from A since they already exist in B.

I want to force Lightroom to import them even though they already exist in B.  Renaming doesn't seem to help.  Does anyone know how to do this.

(Why do I want to import pictures already in the destination catalog?  I want to preserve their edits.  But, more important, I just want to avoid the big job of hunting down all the pictures on the destination catalog and moving them to the folders I want them to be in.)

Thanks all

David