The biggest problem with forced inducted or highcompression LA's is the head bolt arrangement. It's tough keeping a head in place with only 10 head bolts.
and at the same time, look at the sb mopar in early 70's [lil use but still]nascar, ford is the same boat, but there isn't constant issue with only having 4 bolts around the cylinder, but still can come into play at some point maybe.
I believe the biggest obstacle is the smaller main caps that will crack or are prone to at that level, they found this out in the 80's with mopar performance 318 race blocks that would 340 bore, but still had regular 318 main caps.
the way the mains are loaded, it would probably be the no.1 main that gives 1st.
I've heard 500-550 is the limit anf depends on the compression [cyl wall splitting] and parts weight etc..
I think the better question would be 'how long will it last beyond 600 hp'
jmo