The journey from Upleta to Guwahati is a long one, covering about 2500 km. You should travel to Ahmedabad or Rajkot to catch a train to Guwahati. The route involves a long journey across the country. The total travel time is around 50 to 60 hours by train. You will travel from the western coast to the northeastern region of India.
Total Distance: Driving distance 2500 km, straight-line air distance 2000 km.
This is a very long journey; consider breaking it up.
October to April for pleasant weather.