You posted your question in the Apologetics section of this forum, so I recommend (as an apologist) that you keep it. The KJV is highly regarded among many protestants (and not rejected outright by any that I know of), so apologetical ministry to them is often more effective when Biblical citations are from the KJV. You might need to translate NAB passages to the “language” that they speak to achieve the greatest result.
Also, a number of good Bible reference tools (such as Strong’s Concordance and Lexicon) are keyed to the KJV. I’m not aware of any tools such as Strong’s Lexicon that are keyed to the NAB. I do much language research in KJV and convert.
But, if you are determined to get rid of it, I recommend donating it to Goodwill or something similar. Maybe it will do somebody some good. I know the KJV is incomplete (lacking many books) and contains thousands of errors in translation, but the KJV has inspired many people to Christ in some form or another. Better something than nothing.