We have older manuscripts, but these are rife with errors. That's why the BMT is better because even comparing it to the oldest texts extant they are more accurate. The scriptures are consistent. They came out by accident to just the right number as referenced. I doubt anything that "differs" as you say would change the truth of scripture an iota. It would just be more gnats for you to strain. Nothing more.
Age is also not to ever be confused with accuracy, no matter what the manuscript. Start here and work your way out. (Quoted without permission.)
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"The Codex Sinaiticus has been corrected by so many hands that it affords a most interesting and intricate problem to the palaeographer who wishes to disentangle the various stages by which it has reached its present condition...." (Codex Sinaiticus - New Testament volume; page xvii of the introduction).
...(T)here is a scribal problem with this codex and it is a BIG problem. Tischendorf identified four different scribes who were involved writing the original text. However, as many as ten scribes tampered with the codex throughout the centuries. Tischendorf said he "counted 14,800 alterations and corrections in Sinaiticus." Alterations, more alterations, and more alterations were made, and in fact, most of them are believed to be made in the 6th and 7th centuries. "On nearly every page of the manuscript there are corrections and revisions, done by 10 different people." Tischendorf goes on to say,
"...the New Testament...is extremely unreliable...on many occasions 10, 20, 30, 40, words are dropped...letters, words even whole sentences are frequently written twice over, or begun and immediately canceled. That gross blunder, whereby a clause is omitted because it happens to end in the same word as the clause preceding, occurs no less than 115 times in the New Testament."
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Older is not better.
I won't even bother to go into detail how screwed up MS69 is (which is one of Erasmus' sources for the Textus Receptus and eventually the KJV).
"A 15th Century manuscript, MS 69 was not very old (it is dated between 1465-1472) at the time of Erasmus and the margin corrections pre-dated the first edition of his Greek New Testament in 1516. It is also riddled with errors. According to F. H. A. Scrivener's, An Exact Transcription of Codex Augienses (1859) there are 74 omissions of various sorts along with numerous interrupted words."
Dr. Leslie McFall has a nice website also and explains this stuff a lot better than I can. Not that you care.