like some one else said.
At the 900hp (easier said than done) or (before in my case) most hit a wall on hp limit with a good effort Indy stuff..
if one built the same "good effort" engine using the B1 Original heads (not even M1MC's) One would expect to accomplish at least top hp in Indy's case and more.

And just because this "guy" or "that guy" makes great B1 power and making stock blocks live a happy life doesnt mean anyone can throw a engine together and do the same.
Its hard to act surprised or be upset when during the first season, it splits a cylinder wall or cracks the main webbing and thrashes the whole engine.