There's a group on Facebook called "RWD BOOSTED MOPAR MUSCLE" where quite a few people share details about their high hp small blocks.
Many over there are pushing their stock block beyond what is conventionally considered "safe" or "reliable".
On the other hand there is also a lot of anecdotal info on forums of people who have had/seen blocks fail at around 600hp too.
To me this indicates that there is no definitive answer as to what works and what doesn't, or how reliable you can expect X combination to live at Y horsepower.
But IMO if you push your OEM 360 block past 600hp you should anticipate that at any moment it could potentially suffer an instantaneous unscheduled disassembly.