Hey Akshaya!

A normalised score of 70+ is enough to get a good stream in sastra university , as per the previous year cutoffs. But mechanical engineering is the most preferred course at sastra university and the cutoffd for this increase every year , so if this year ,the cutoffs don't increase by a large extent  , you have sufficiently good chances of getting a seat in mechanical engineering . But i must say , you are not on a safe side. 

To know the names of other colleges where you can expect a seat , use JEE MAINS COLLEGE PREDICTOR tool:

Https://engineering.careers360.com/jee-main-college-predictor

Hope it helps!