Factory old iron just can't compete ... ??
We had a thread not to long ago about the hp limit of a sbm, never got a definitive answer, there's more than enough 500-550 hp sbm engine's out the to believe that's relatively safe, I think there's seems to be a decent amount of 550-650 hp sbm out there without hearing too many horror stories to think these numbers if done right are reasonably ok. Problem is above that there's just not enough 700 + hp NA engines out there, same with 1000 + hp turbo, blown, nitrous etc.. So it's up in the air.
As for bbm you hear of a decent amount of 700-800 hp examples to believe that's probably ok.
Problem is you need enough people to build higher hp engines to know for sure. And for people to do that you need affordable ootb parts (mainly heads) that get 600/700/800+ hp.
The new engines start with heads that rival most race only heads for older engines plus people slapping on turbos etc.. On top of that has allowed them pretty quickly find the weak spots.