Peak HP from LA block w/ no problems

For anyone who has built a killer STREETABLE smallblock based on early 340 or 360 block. Up to what HP (no guesses, documented) did you make safely?
One reference i have says "no more than 450 HP safely" from a factory LA block. Im assuming they mean for extended durations like circle track or something, not street or occasional strip.
Im mostly interested from a reliability standpoint. I'd rather not build something I'll soon break.