If you're trying to separate yourself from the pen-name you first sold that story under, why would you do this?
If anyone spots that it was published before (and people notice things, you know) it's going to appear that your new name has plagiarised the story.
You'll then have to explain what you did, and by doing so you'll establish a connection between the two names and, what with the internet being forever, you'll be stuffed.
It seems like a bad idea to me.
However, you probably could do this if you wanted, although you'd have to tell the new publisher that it was previously published under a different name.