...66 books but not the 73? what gives? ...
Yep, as the Bible itself gives:
For instance (shown from the KJB and DR; Douay Rheims Online, 'DR' from here on), there was already the "church in the wilderness", which was with Moses, children of Israel:
Act. 7:38 KJB This is he, that was in the church in the wilderness with the angel which spake to him in the mount Sina, and with our fathers: who received the lively oracles to give unto us:
Act. 7:38 DR This is he that was in the church in the wilderness, with the angel who spoke to him on mount Sina, and with our fathers; who received the words of life to give unto us.
Additionally, Paul wrote that the "oracles of God" were committed unto the Jews, and Peter also mentions this:
Rom. 3:1 KJB What advantage then hath the Jew? or what profit is there of circumcision?
Rom. 3:2 KJB Much every way: chiefly, because that unto them were committed the oracles of God.
Rom. 3:1 DR What advantage then hath the Jew, or what is the profit of circumcision?
Rom. 3:2 DR Much every way. First indeed, because the words of God were committed to them.
Heb. 5:12 KJB For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat.
Heb. 5:12 DR For whereas for the time you ought to be masters, you have need to be taught again what are the first elements of the words of God: and you are become such as have need of milk, and not of strong meat.
1 Pet. 4:11 KJB If any man speak, let him speak as the oracles of God; if any man minister, let him do it as of the ability which God giveth: that God in all things may be glorified through Jesus Christ, to whom be praise and dominion for ever and ever. Amen.
1 Pet. 4:11 DR If any man speak, let him speak, as the words of God. If any man minister, let him do it, as of the power, which God administereth: that in all things God may be honoured through Jesus Christ: to whom is glory and empire for ever and ever. Amen.
Now the DR here (1 Pet. 4:11), inserting a comma changes the meaning, from the text itself as from saying (KJB) that when men speak they are to speak what the scriptures say, and the Jesuit (DR) makes it to mean that whatever a man speaks, that is "the words of God", thus eliminating the foundation from the text itself, to men (in what they say).
The entire OT texts were already 'canon' in the days of Jesus, none of which included any of the apocrypha (aka 'catholic deuterocanon'). Jesus Himself identified the texts:
Luk. 24:44 KJB And he said unto them, These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me.
Luk. 24:45 KJB Then opened he their understanding, that they might understand the scriptures,
Luk. 24:44 DR And he said to them: These are the words which I spoke to you, while I was yet with you, that all things must needs be fulfilled, which are written in the law of Moses, and in the prophets, and in the psalms, concerning me.
Luk. 24:45 DR Then he opened their understanding, that they might understand the scriptures.
Jesus identified the beginning and the ending of the OT among the children of Israel:
Mat. 23:35 KJB That upon you may come all the righteous blood shed upon the earth, from the blood of righteous Abel unto the blood of Zacharias son of Barachias, whom ye slew between the temple and the altar.
Mat. 23:35 DR That upon you may come all the just blood that hath been shed upon the earth, from the blood of Abel the just, even unto the blood of Zacharias the son of Barachias, whom you killed between the temple and the altar.
Luk. 11:50 KJB That the blood of all the prophets, which was shed from the foundation of the world, may be required of this generation;
Luk. 11:50 DR That the blood of all the prophets which was shed from the foundation of the world, may be required of this generation,
Luk. 11:51 KJB From the blood of Abel unto the blood of Zacharias, which perished between the altar and the temple: verily I say unto you, It shall be required of this generation.
Luk. 11:51 DR From the blood of Abel unto the blood of Zacharias, who was slain between the altar and the temple: Yea I say to you, It shall be required of this generation.
This is an important statement by Jesus since, it gives two 'book ends' on the prophets, "Abel" unto "Zacharias", which was the "A" to "Z" of the OT, since according to the children of Israel's reckoning, Chronicles was the last bookof the Tanakh (OT) [Torah (Gen. to Deut.), Prophets (Jos. to Mal.), Writings (Psa. to 2 Chron.)]:
2 Chron. 24:20 KJB And the Spirit of God came upon Zechariah the son of Jehoiada the priest, which stood above the people, and said unto them, Thus saith God, Why transgress ye the commandments of the LORD, that ye cannot prosper? because ye have forsaken the LORD, he hath also forsaken you.
2 Chron. 24:20 DR The spirit of God then came upon Zacharias the son of Joiada the priest, and he stood in the sight of the people, and said to them: Thus saith the Lord God: Why transgress you the commandment of the Lord which will not be for your good, and have forsaken the Lord, to make him forsake you?
2 Chron. 24:21 KJB And they conspired against him, and stoned him with stones at the commandment of the king in the court of the house of the LORD.
2 Chron. 24:21 DR And they gathered themselves together against him, and stoned him at the king's commandment in the court of the house of the Lord.
2 Chron. 24:22 KJB Thus Joash the king remembered not the kindness which Jehoiada his father had done to him, but slew his son. And when he died, he said, The LORD look upon it, and require it.
2 Chron. 24:22 DR And king Joas did not remember the kindness that Joiada his father had done to him, but killed his son. And when he died, he said: The Lord see, and require it.
I would recommend a helpful webpage with further detail - How Many Books Are In The Old Testament?
Peter also already knew (well before AD 90, sometime circa AD 65-68, since the epistles mention Peter's nearing death (2 Pet. 1:14) what the 'scriptures' were in regards to Paul's epistles (14 letters, Romans to Hebrews; ie, Romans, 1 Corinthians, 2 Corinthians, Galatians, Ephesians, Philippians, Colossians, 1 Thessalonians, 2 Thessalonians, 1 Timothy, 2 Timothy, Titus, Philemon, Hebrews):
2 Pet. 3:16 KJB As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
2 Pet. 3:16 DR As also in all his epistles, speaking in them of these things; in which are certain things hard to be understood, which the unlearned and unstable wrest, as they do also the other scriptures, to their own destruction.
The Holy Scriptures are inspired of God, and are therefore, not 'catholic', but rather is God's word, the "word of God" (Jhn. 10:35):
2 Tim. 3:15 KJB And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus.
2 Tim. 3:15 DR And because from thy infancy thou hast known the holy scriptures, which can instruct thee to salvation, by the faith which is in Christ Jesus.
2 Tim. 3:16 KJB All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness:
2 Tim. 3:16 DR All scripture, inspired of God, is profitable to teach, to reprove, to correct, to instruct in justice,
2 Tim. 3:17 KJB That the man of God may be perfect, throughly furnished unto all good works.
2 Tim. 3:17 DR That the man of God may be perfect, furnished to every good work.
2 Pet. 1:21 KJB For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.
2 Pet. 1:21 DR For prophecy came not by the will of man at any time: but the holy men of God spoke, inspired by the Holy Ghost.
The "scriptures" were already well known in Jesus' day in regards the OT, as per:
Dan. 10:21; Mat. 21:42. 22:29, 26:54,56; Mar. 12:10,24, 14:49, 15:28; Luk. 4:21, 24:27,32,45; Jhn. 2:22, 5:39, 7:38,42, 10:35, 13:18, 17:12, 19:24,28,36,37, 20:9; Act. 1:16, 8:32,35, 17:2,11, 18:24,28; Rom. 1:2, 4:3, 9:17, 10:11, 11:2, 15:4, 16:26; 1 Cor. 15:3,4; Gal. 3:8,22, 4:30; 1 Tim. 5:18; 2 Tim. 3:15,16; Jam. 2:8,23, 4:5; 1 Pet. 2:6; 2 Pet. 1:20, 3:16
In fact, how could Jesus say to the Jews,
"Search the scriptures" that prophesied of Christ Jesus, if the Jews had no idea what
"the scriptures" were, to search, and every man had their own idea as to what constituted them?
Jhn. 5:39 KJB Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
Jhn. 5:39 DR Search the scriptures, for you think in them to have life everlasting; and the same are they that give testimony of me.
In fact, none of the apocrypha ('catholic deuterocanon'), are cited by any of the Apostles in the NT as fulfilling prophecy (some might attempt to point to Jud. citing so-called 'Enoch' (pseudopigrahpon), but that is another matter, and it doesn't either, as both are referring to Gen. and Deut.).
The angel Gabriel, in the days of Daniel was able to explain to Daniel, the prophecies given him from the very texts which existed before 'Daniel' was written (basically Gen. to Jer. (maybe some Eze.) and others hadn't yet been written by then, such as Ezr., Neh., Est., etc. and some of the 'minor prophets'):
Dan. 10:21 KJB But I will shew thee that which is noted in the scripture of truth: and there is none that holdeth with me in these things, but Michael your prince.
Dan. 10:21 DR But I will tell thee what is set down in the scripture of truth: and none is my helper in all these things, but Michael your prince.