I would buy a lighter, more modern rotating assembly, then update the heads. Even ported Eddies would have way more potential than what you have, they go over 300 easily with modest work.
Then if the above doesn't get you there, you are way better equipped to maybe spray a more modest amount( onto better parts) to reach your goal.
To me, a good shortblock is the foundation to any attempt to make even half way serious power.