Eesa,
I just realized something, that I don't know why it didn't sink in before. It would do absolutely no good -- with respect to Islam that is -- for Christians to be in possessions of the original autographs of the Bible. As far as Islam is concerned, even what was originally written down could itself be tainted and you would be under no compulsion to accept it as the accurate record of Jesus revelation or any other revelation of God. It would still be just as you said above --"The process that allowed some mistakes to enter the Biblical Writing is one that doesn't just dissapear when a part of the text agrees with the Qu'ran." -- unless it were penned by Jesus himself. And even if that existed, but there were differences between that and what was written in the Qur'an, Islam would just argue that it was not the work of Jesus based on the belief that the Qur'an was authentic and thus anything else that disagreed must be what is in error. There is no proof that anyone could ever to a true believe in the Qur'an that anything else could be valid if it disagreed with the Qur'an. It is not a question of proof or reason, it is purely a question of faith.