There are many good medicaal colleges present in Bihar and the competition is quite tough.If you are from Bihar you can apply under the 85% state reservation. It is quite difficult to predit the marks to get admission with the ever increasing number of students and changes in the difficulty level to the examination.
But if we refer to the previous year cuttoff and scores

For general category you need to score more than 550.
For obc there is not much difference.You need to score more than 520 to get a good college.
For SC you will have to score more than 450. 
And for ST more than 420 will be fine.

If you need any further details regarding this you can refer to the link provided below:
https://medicine.careers360.com/articles/neet-cutoff-bihar