How substantive do you believe the difference between the Douay - Rheims and the King James versions to be with regard to the New Testament?
The deuterocanonicals teach Catholic doctrine, and for this reason they were taken out of the Old Testament by Martin Luther and placed in an appendix without page numbers. Luther also took out four New Testament books -- Hebrews, James, Jude, and Revelation -- and put them in an appendix without page numbers as well. These were later put back into the New Testament by other Protestants, but the seven books of the Old Testament were left out. Following Luther they had been left in an appendix to the Old Testament, and eventually the appendix itself was dropped (in 1827 by the British and Foreign Bible Society), which is why these books are not found at all in most contemporary Protestant Bibles, though they were appendicized in classic Protestant translations such as the King James Version.
The reason they were dropped is that they teach Catholic doctrines that the Protestant Reformers chose to reject. Earlier we cited an example where the book of Hebrews holds up to us an Old Testament example from 2 Maccabees 7, an incident not to be found anywhere in the Protestant Bible, but easily discoverable in the Catholic Bible. Why would Martin Luther cut out this book when it is so clearly held up as an example to us by the New Testament? Simple: A few chapters later it endorses the practice of praying for the dead so that they may be freed from the consequences of their sins (2 Macc. 12:41-45); in other words, the Catholic doctrine of purgatory. Since Luther chose to reject the historic Christian teaching of purgatory (which dates from before the time of Christ, as 2 Maccabees shows), he had to remove that book from the Bible and appendicize it. (Notice that he also removed Hebrews, the book which cites 2 Maccabees, to an appendix as well.)
To justify this rejection of books that had been in the Bible since before the days of the apostles (for the Septuagint was written before the apostles), the early Protestants cited as their chief reason the fact that the Jews of their day did not honor these books, going back to the council of Javneh in A.D. 90. But the Reformers were aware of only European Jews; they were unaware of African Jews, such as the Ethiopian Jews who accept the deuterocanonicals as part of their Bible. They glossed over the references to the deuterocanonicals in the New Testament, as well as its use of the Septuagint. They ignored the fact that there were multiple canons of the Jewish Scriptures circulating in first century, appealing to a post-Christian Jewish council which has no authority over Christians as evidence that "The Jews don't except these books." In short, they went to enormous lengths to rationalize their rejection of these books of the Bible.
It is ironic that Protestants reject the inclusion of the deuterocanonicals at councils such as Hippo (393) and Carthage (397), because these are the very same early Church councils that Protestants appeal to for the canon of the New Testament. Prior to the councils of the late 300s, there was a wide range of disagreement over exactly what books belonged in the New Testament. Certain books, such as the gospels, acts, and most of the epistles of Paul had long been agreed upon. However a number of the books of the New Testament, most notably Hebrews, James, 2 Peter, 2 & 3 John, and Revelation remained hotly disputed until the canon was settled. They are, in effect, "New Testament deuterocanonicals."
While Protestants are willing to accept the testimony of Hippo and Carthage (the councils they most commonly cite) for the canonicity of the New Testament deuterocanonicals, they are unwilling to accept the testimony of Hippo and Carthage for the canonicity of the Old Testament deuterocanonicals. Ironic indeed!