The journey from Imphal to Surat covers roughly 2800 km. You must first reach Guwahati or fly from Imphal. Flights from Imphal to Surat usually connect through Delhi or Mumbai. Trains from Guwahati to Surat are long-distance and require a change.
Total Distance: 2800 km by road, 2300 km air distance.
This is a very long journey; ensure you have a confirmed berth.
Delhi is the most convenient hub for this connection.
October to March for pleasant weather.