Total seats at IITs is just 6895 which is quite near to you rank. If some students dont show up for counselling than also your most likely college would be new IITs or IT-BHU or ISM Dhanbad where you wont wish to go ( i also recommend that ). Taking any course at new IITs just on the name of IIT is stupidity as they are not stable and facing a lot of problems regarding foodin and lodging ( being mentored by the older IITs ).
Considering the other option i.e. BITS, you have a bright career there. This college is behind only 3 IITs in ranking and provides a secure future. you can opt for chemical or civil there. Opting Chemical would be better if you have interest( my personal view).
Hope you take the right decision.