They were most certainly NOT in their original forms at the time of Rasulullah, salallahu alaihi wa salam. baring the remote possibility of some text squirled away somewhere remote.
This is a frequently heard assertion but it is untrue, though the Injeel is certainly corrupt now, it was corrupt then as well, and there are copies of manuscripts dating from that time. The books of the Gospel
As for the modern Jewish version of the Taurat, based on the Masoretic text, it has been better preserved than the Injeel since that period, and it was already corrupt in that age and the version we have today is pretty consistent with the version then, the modern torah, or "tanakh" (interestingly enough, called by the early Rabbis the Miqra, a word that is a cognate of Quran) was compiled in its present form by about 200 AD, 400 years before the time of the Sahabah (ra)
The modern Samaritan's version of the taurat is arguably a more ancient version than that of the modern Jews (and thus likely to be better preserved since they rejected the Talmudic innovations that the Judeans brought with them from Babylon, preferring closer to the original teachings of Musa (as) to remain to to authenticity) but it is still rather close to the Masoretic text.
The general gist is that the Taurat of the Samaritans, the Jews, and the Christian Old Testament today is pretty close to if not identical in some cases with that recited by the Samaritans, Jews, and Christians during the first century of Islam.
As for the Injeel of the Christians, the numerous differing versions (from the Syrian's, the Egyptian Copts, the Ethiopians, the Eastern Orthodox and the Western Christians) they all had similar levels of corruption in the first century of Islam and there are manuscripts backing this up.
So they were all reciting texts then similar to the texts their ancestors read and recite today. We consider all of it corrupt. And marriage with Kitabis was permissible then, so what has changed in this one aspect?