Hi

We could have helped you in more better way if you would have told us your branch. Branch plays a major role in PSU. In mechanical branch the compitition is very high compared to instrumentation. 

But anyways, with 49 marks you have very less chanes of getting into PSUs. And that too in general category.

You can do one thing many IITs and IISc recruit GATE qualified graduates as JRFs ( Junior Research Fellow ).  You can apply for that. You will be paid 20K per month.