NITs don't provide aerospace engineering branch.

You can take admission in IIT's for Aerospace branch through JEE Advanced. 

In order to appear for JEE Advanced you have to qualify JEE Main exam first. 

JEE Advanced maximum are not defined :

Maximum Marks vary every year like below:

2017- 366 

2016- 372

2015 - 504

2014 - 360

So, it is difficult to predict marks as exam pattern and marks change every year.

You can check the cut off rank from the given below link

https://engineering.careers360.com/articles/iits-cutoff-for-b-tech-aerospace-engineering

Good luck!!