500 vs 512 from 400ci

I remember talking to someone at Koffels 3 or 4 years ago. They advised me to get the 230 heavy casting block and claimed they made 900hp engines using those.
I wanted to either use cross bolted main caps or BCR griddle with aluminum caps.
I will probably also half fill it as I did my current 530 casting block.
I've never seen a 900HP engine come off that dyno that backed the number up. Things may have changed recently however.