I've seen a few blocks crackalso, round the 300-350rwkw mark.
however key point was they were stock motors/blocks.
I've not seen however, a grout/prepd stock block crack upto 440rwkw.
Now, you have others here as well like Matt, Aaron, Marko, Steve, Paul etc running 2.8-3lt... And 400-450rwkw. None have split a prep'd block either yet...
Lots of guys running 10s and 9s in street driven cars that aren't totally filled etc.
End of ghetto day you can never say
it can't happen, but i think if IT IS gonna happen, it will happen REGARDLESS if you have this 1200 part or not as its potentially more to do with block casting/conditioning and the prep supporting a block that is
less likely to crack in the first place.