I have heard that the Oral law tells us which vowels go where in the Torah and how the words were divided, since originally the Torah was written without spaces between words. Can you provide any sources for this?
Perhaps you are referring to a statement of the Vilna Gaon in his book Kol Eliyahu (end of V’zos Ha’bracha), which records his understanding of a certain discussion in the Talmud to mean, that the last eight verses in the Torah (which discuss the death of Moshe Rabeinu, Moses) were originally transcribed by Moshe in a mixture of letters (ie. all of the letters which comprise these verses as we have them were written by Moshe in the Torah. However, these letters were mixed around in a way that would not form understandable words or phrases. Alternatively the Vilna Gaon may have meant that all of the letters were in their proper places, but the spaces were not in the places that we have them now). After Moshe died, Yehoshua (Joshua) was given the duty of rearanging the letters in their proper places (or alternitively, to put the spaces in the correct places) .
The Gaon adds that before the world was created the Torah existed, albeit in a drastically different form. The Torah had all of the same letters that our Sefer Torah has, yet all of the letters were not seperated by the spaces that we have. Rather, they were seperated in different places, thus forming an extremely long strand of different combinations of G-d’s names. Only when the Torah was given to the Jewish people were the spaces between the letters changed to create a comprehensible, “down to Earth” Torah. The eight verses written by Moshe, writes the Vilna Gaon, were a part of this original Torah. See also the introduction to the Torah of the Ramban (Nachmanides).