You can assume about 70-80 mins as the potential transfer time for an average passenger (intl/dom) at Delhi. However, it is a cinch.

What can work for you is that AI may transfer you airside via car (it happens often on Jet/AI).

What can definitely work against you is that you may 90% touch down on the new runway, spend 15 mins taxiing to the domestic side.

Couple in the fact that most aircraft are a wee bit delayed by noon anyways and you have a big problem on your hands.

So transfering at Delhi - be safe and keep 2 hours in hand. Once the new T3 opens, you may definitely do it in under 60 mins.