I just paid $300 for a short block and a set of heads. I am happier then heck. Engine was seized and was previously rebuilt so I just pulled it apart and sent it off to the shop to get cleaned and mag'd.
Even though the block and heads are a 2V you can still build a monster engine. I just got my 2V back from the shop and it dyno'd at 441 hp @ 6000 rpm. It cost me a lot and I replaced almost everything except the block.
All Cleveland blocks are rated for around 600hp and at that they only need 2 bolt mains. If you go any crazier than that your should consider getting a machinist to drill in another bolt for you and turn your 2 bolt mains into 4 bolt. There is lots of room for the additional bolt.
The shop gave me a quote of $1800 to redo the heads to flow enough air for 450 hp which I find very reasonable but I opted for aluminum heads to drop some weight instead. Not sure how much air you can push through the factory intake manifold but for $500 USD you can get a very nice dual plane intake that will spread the torque around where you need it. Make sure you watch the height of the deck on the intake to ensure it still fits under your hood. Whichever direction you decide to go make sure you replace the valves, the factory valves are welded and are a known failure point. Go with solid valves.
As a final point, don't start buying parts by piecemeal, plan the whole build first so all of your parts work together as a system. Huge ports on a head are no good if you use factory exhaust. And even if you get headers, make sure you choose the length to correspond with where you want your power range, long-tubes for power at high rpm and shorties for lots in the low range.
