If you go to a school of divinity they will date the Gospel of John at around 120 CE. Not only that but there is almost no argument that the Gospel of John was originally written in Greek which also points to a later than contemporaneous writing. I would love to see ANY proof you have that John was written before the 60's which is where to oldest version of Mark and Matthew date from. There are absolutely NO Gospels found in Aramaic which would strengthen any claim of contemporaneous writing.
The New Interpreter's Dictionary of the Bible: Volume 3 Abingdon Press, 2008. p. 362 "Presently, few commentators would argue that a disciple of Jesus actually wrote the Fourth Gospel,..."
"Although ancient traditions attributed to the Apostle John the Fourth Gospel, the Book of Revelation, and the three Epistles of John, modern scholars believe that he wrote none of them." Harris, Stephen L., Understanding the Bible (Palo Alto: Mayfield, 1985) p. 355
Marilyn Mellowes The Gospel of John From Jesus to Christ: A Portrait of Jesus' World. PBS 2010-11-3. "Tradition has credited John, the son of Zebedee and an apostle of Jesus, with the authorship of the fourth gospel. Most scholars dispute this notion;..."
However, there are two notable exceptions:
Blomberg, Craig (2009-08-01). "The Gospel of John". Jesus and the Gospels (2nd ed.). Nashville: B & H Publishing Group. pp. 197–198. ISBN 0805444823. "All this adds up to strong circumstantial evidence for equating the beloved disciple with the apostle John."
Carson, D A (1991). "The Authorship of the Fourth Gospel". The Gospel According to John. Grand Rapids: William B Eerdmans Publishing Company. pp. 68–69. ISBN 0802836836. "[Denying Johannine Authorship] Also requires their virtual dismissal of the external evidence. This is particularly regrettable. Most scholars of antiquity, were they assessing the authorship of some other document, could not so easily set aside the evidence as plentiful, consistent and plainly tied to the sources as is the external evidence that supports Johannine authorship."
I believe you will have difficulty finding many more that agree that John was THE author.