Looking at the past trends and veiws of my collegues reagrds IIT R, it has loosing it's sheel and that's why it's ranking is genting worsen year by year.

Hence you can expect a seat at EC or EE branch within 400 SC rank. But I would like to recommend you to have an SC rank of 350 to be on safe side.

Also regarding marks, this I can't say much 

Still according to me 30-35 marks above the cut-off would be sufficent to come within the 350 SC rank.