Chandragupta Maurya or Chandragupta?

Reader Kedar asked two questions recently

1. There is a huge gap between Mahabharata (3100 BCE, 2450 BCE, 1500 BCE) and the Mahajapadas. What happened there?
2. Who was the contemporary of Alexander of Macedonia? Chandragupta Maurya or the Guptas? Do Mahavira, Buddha and Adi Shankara belong to an earlier period?

We will look at (2) today and deal with (1) later.
At the International Conference on Indian History, Civilisation and Geopolitics 2009, Dr Subramanian Swamy gave the valdedictory speech on the need to defalsify Indian history. In this speech, Dr. Swamy stated that most dates  related to Indian history – Rigveda, Mahabharata, Buddha, Asoka —  are wrong. This happened because European historians identified Sandrocottus, mentioned by Megasthenes, as Chandragupta Maurya. This Sandrocottos was a contemporary of Alexander and from associated calculations, the date of Chandragupta Maurya’s coronation was found. Based on this point, Asoka’s corononation was calculated, so was the time of Buddha.
But according to Swamy,  the correct dates are as follows

However, on the basis of these calculations we can say that Gupta Chandragupta was “Sandrocottus” c.327 B.C. His son, Samudragupta, was the great king who established a unified kingdom all over India, and obtained from the Cholas, Pandyas, and Cheras their recognition of him. He also had defeated Seleucus Nicator, while his father Chandragupta was king. On this calculation we can also place Prithu at 6777 B.C. and Lord Rama before that. Derivation of other dates without discussion may also be briefly mentioned here: Buddha’s Nirvana 1807 B.C., Maurya Chandragupta c. 1534 B.C., Harsha Vikramaditya (Parmar) c. 82 B.C.[Non-random-Thoughts: ‘De-falsify Indian history’ — Dr Subramanian Swamy]

Thus, a case is presented that Western historians distorted Indian history and it is our responsibility to correct it. So let us accept for a moment that Buddha lived in 1807 BCE. We don’t have archaeological evidence of the cities and kingdoms mentioned in Buddhist texts dating to that period.
If Rama lived in 6777 BCE, he belonged to the Neolithic age and would have fought with axe heads and chisels. This Rama would be vastly different from the one portrayed in Ramayana, like King David. The Tel Dan Stele mentions David’s existence, but archaeology has found that he would have been not a king, but a petty warlord of a small chiefdom with few settlements. So did this Neolothic Rama’s exploits survive as a mnemohistory, like how David’s lives in the Torah?
Whether due to colonial bias or not, we have certain dates and there is an effort to propose new ones. But these new ones have to take into consideration the social order of the time and also be backed up by archaeology.