Marks is never a good indicator for AIIMS to judge amission. It all depends on percentile. I remember the year i was admitted to AIIMS the highest scored was 136. A percentile of 99.5% and above is required to be in AIIMS for OBC as a safe mark thats what can be said. Marks fluctuate depending on shift- afternoon or morning as well as level of questions.

Try attempting 180+ and by that equation even with a negative of 20 approx you may get 140+.

Best of Luck 

For AIIMS DELHI 165 is the safest score but 140–145 is also pretty much a good score. you will have the option of choosing any of the New AIIMS but not delhi . 

 Just to qualify the exam..

General category should have more than 50%

OBC should have atleast 45%

SC and ST category should have atleast 40%  

And for delhi aiims improve the scale as per your category.