Here are the necessary PODs:
Large Indo-Aryan migration into China. There were some. Probably limited to Khotan and Sogdia as even Tocharian City states were fully Buddhist and even the former two were Buddhist with some Hindu influence. If you consider Buddhism as a subset of Hinduism as many do,then possible with this conditions if these spread the faith or colonize and make a stable Empire. If you could have Indo-Aryans settle in the Xinjiang and the greener regions in the West Central China,could be possible though quite difficult to achieve.
Another is of a Missionary oriented Hinduism. Difficult to achieve with that core theology. This again needs a POD somewhere near the Indo-Aryan migrations as Hinduism became a religion with ethnic aspects harder to reform as time went on till crystallizing at around the Gupta era. So what all could be possible at that time and any major reform possible in the eras inbetween has to be investigated.
The geography was too much a barrier to have a free exchange of people from both sides which could spread the religion otherwise. That anyway is ASB.