5,500 + Block machining, which isnt much really, but to rev it to 8,000rpm you would need the billet caps and girdle, So no idea how much that is, + head work to be able to take advantage of the extra 400cc + cams + larger Valves + springs/retainers.
Just buying the rotating assembly is one thing, actually using it effectively is another.
Eg I was looking at building a 408cube stroker out of the cleveland I have, but ive decided against it because I want to use the standard cast iron heads etc, so there is no point to having an engine that big if the heads cant flow enough to take advantage.
A little different when a turbo is involved but the same basic gist still applies.