From looking at engines all over (btw I am not an expert or a gear-head, as yahh know just an run of the mill idiot) since you have all he peripherals on the mills you have now I would buy the 509 long-blocks that Teague has for $9995. They are Dynoed conservatively at 575HP, naturally aspirated and all the attachment you need you should have on the blocks you have now. Transferring all and mounting should not be that big of a deal. I have talked to them about three weeks ago and they had five blocks in stock. I think they are warranted for a year also.
Again I have nothing to do with that shop. Bob Teague has a good reputation on the board.
It might be worth your time to at least investigate.
You might of tough of that already, hope this helps and this is only my opinion after looking around for Marine Long Blocks for sh!ts and giggles. I'm positive some people will enlighten me with better suggestions but this theory resonates well with my limited mental capacities!