The Chola Kingdom existed at the time of the Mauryan Empire and was one of the three Tamil dynasties that lasted for centuries. The Pandyas and the Cheras were the other two. After a period of being vassalised by the Pallavas, Cholas re-emerged around 850 BCE and then entered their Imperial period before the final collapse in the second half of the thirteenth century. In total the Chola dynasty lasted for almost 1500 years with ups and downs including Imperial status at times and periods of vassalage and independence at other times. The Pandyas who were their rivals often, also lasted for nearly 1700 years and outlasted the Cholas defeating them, but never rose to the Imperial heights as the Cholas did.
Probably by 1970 (depending on your definiton of global superpower).Honestly, better economic policy from India as opposed to the Nehru-Gandhi License Raj might mean India as a global superpower by 2010.
I did one where Rajaji, instead of Nehru, becomes India's first Prime Minister, meaning no sclerotic economic planning.
It was quite implausible for Rajaji to be chosen as the Prime Minister at the time of Independence. Though he was one of the senior leaders of the Congress, he was not a popular leader like Gandhiji or Nehru or Bose. If the Congress Party was given freedom to choose the leader the man who was likely to be chosen was Sardar Patel, as he was a master organiser who had the party under his firm control. But Gandhiji named his favorite disciple Jawaharlal for the post and Sardar was too obedient a shishya to question his Guru.
If Sardar Patel was the Prime Minister, Rajaji might have become his Lieutenant as ideologically they were closer and on the opposite side of Jawaharlal Nehru. In course of time Nehru would have become the leader of the left wing in the Congress and the right wing which was dominant would have forced him out of the Party. A two-party system might have developed in the initial decades of the democratic India.