Hey,

 Firstly congratulations for securing this rank. It's a great thing.

Now the last year's cut off rank for IMS, BHU was 761 for unreserved category. And that of GS medical College, Mumbai was 1458. So considering that you have good chances of admission in both the colleges. But in my opinion IMS, BHU will be far better for MBBS which is also visible from the last merit ranks admitted in 2018. Now it's. Upto you completely.

Hope you have a great future ahead