There is no online text. You will have to download the book (pdf) from here:
Here is the complete Mahabharata translated into English prose directly from the original Sanskrit text by Pratap Chandra Roy. Download the complete PDF e-book here for free.
holybooks.com
If you want to look that way, the NE people have vastly different appearance than other Indians. Does this mean they were natives? As I posted the snippet above, Chins, Kiratas (hybrid between Chins & Naras/Indians) existed even during Mahabharatha and lived with others. In fact, the kingdom of Pragjyotishya (Assam) which were filled with mongoloids (Chins & Kiratas) fought in Mahabharatha on the side of Duryodhana, showing how they were part of Indian empire despite racial difference.
However, even during Mahabharatha times, there was extensive contact between Europe and India. People like Yavanas and other Europeans are mentioned regularly. Naturally, people closer to the borders tend to intermarry and carry the genes across. That is why there is a difference of genes across regions. This does not make anyone outsider or insider/native.
There was no mention of Iranians anywhere. There were Yavanas, Yakshas, Gandharvas, Naras and a few other races. The Huns, Kushans were empires/dynasties of certain kings rather than an entire race. All of them were of a mix of European & Turkic races.
Don't you think it is common sense that people's DNA changes according to region? Do you think the DNA of people in Assam is same as that of Bihar? Does it mean that Biharis are not natives? The DNA of population keeps changing over time as there are intermovements.
Let us take an example: Some Chinese came into Assam, became successful and settled there. Because of their success, people became attracted to them and wanted to have more relationship with them and many of them got multiple wives and produced a dozen children, all of whom were able to become adults due to access to family wealth. Hence their offsprings had higher success in breeding and over time the share of Chinese DNA increased in Assam. About 200 years hence, Assam got 15% of the DNA to be Chinese. Does this mean they are outsiders who invaded Assam? In older times, the population of the world was about 10% of what it is today. So, even if 200-300 people of a community became successful and settled in a place, over 100-200 years, their DNA would become widespread in that region. This in no way means anything.
Pakistan did not exist in the past. Even today, Pakistan has people with vastly different lineage. Baluchistan is mostly Persian Shia, KPK is mostly Afghan. Also, southern Pakistan (Sindh) and Pakistani Punjab was part of Indian empire, not Gandharvas.
That is because in the past Gandharva horses were extremely popular. There are no good varieties of horses in Afghanistan region of Gandhar. The good horses are mainly from Iran & Mesopotamia region. So, even though the Gandharvas existed from today's KPK, they also extended to the West Asia. Ancient Indian texts don't mention the western boundaries of Gandharva lands. Ancient Indian texts only give description of territory within India and not outside it. It only says that Gandharva kingdom existed across the North & Northwest of current day India. But the fact that Gandharvas were known for their horses and also that further west were kings of Yavanas, whom we know to be Greeks whose empire extended till Byzantine. Since no other race is mentioned between Gandharvas & Yavanas, it isonly logical to consider that entire epopulaion of Mesopotamia extending to Central Asia, including Iranians, were Gandharvas.
Also, nowhere in any ancient history before Asura Mahda (Zoroastrianism founder) there was any mention of Iran or Persia. Persia/Iran came to being only because of the cult formed around Asura Mahda. There was no real race of Iranians. Iran is only a political community rather than a race.