NIT Surathkal - National Institute of Technology Mangalore Answered Questions

One can get admission into B.Tech colleges after completing his Diploma through lateral entry. A person who had completed his three years of Diploma can directly enter into 3rd semester B.Tech by writing different entrance exams for different states. Students who enter through lateral entry after Diploma will have the same pattern as that of a normal B.Tech student.
Eligibility for B.Tech after Diploma:
* Students should have completed his 1st-year B.Tech from any recognized university or he should have completed his 3 years of diploma after 10th with a minimum aggregate of 60% marks in science and maths.
*Students who are appearing for final year diploma exam can also apply for lateral entry admission but they have to assure to submit provisional certificate at the time of admission.
Exams that offer lateral entry into B.Tech colleges are JECRC, ECET, LEET, etc.
But one cannot enter into IIT's or NIT's after his diploma because entry into these institutions is based on JEE. They do not offer lateral entry.

You have got good marks, but NIT, Surthkal, Karnataka comes under the top list of NITs.
Not only this, they both are famous for their mechanical branch after NIT, Durgapur and Surat.
So, 139 is not enough as the admission in those NITs starts from 180+ for home quota and 250+ for other state students.
But as you mentioned you are an OBC category student, you have very slim chances to get into it.
I will prefer to give them top priorities in the choice filling.
All the best.