***If you read virtually any KJV, you will find that the passages such as Mark 16:9-20 are in italics, ****
Not so in my Cambridge!
Or English Oxford!
Or the old Collins/ World,
Or (modern) World!
Or American Oxford!
Or any other KJV.
Only my old printing of the RSV has them gone, but they are in the footnotes.
That's because there are 3 standarized texts: The Textus Receptus, which was put together by Erasmus and which the KJV is based on, the Alexandrian Text which is what a lot of modern Bibles are based on, and the Byzantine Majority Text, which not too many translators use, but might be even a better way to go (IMHO).
There's a nice short discussion of standardized texts and why people are unhappy with the Alexandrian text - (biased in favor of the BMT) on this website:
http://www.tricountyi.net/~randerse/BYZmenu.htm
There is an online text - The WEB bible which is a modernization of the ASV using the BMJ as its reference which is something worth looking at - it's also intentionally been made public domain.
http://www.ebible.org/web/indexfr.htm