I currently have a pro street nova with a 427 big block running on pump gas and it's built pretty well. If I had to guess I would say 550 to 600 hp at the wheels give or take some. I am thinking about swapping it out for a 598 BBC for more power when I am at the strip. I know my 427 guzzles gas like it's nothing so I  don't know. The 598 would have more solid parts but I don't know if it would be worth it of if I should just keep my 427.  

If you think you are going to make the car only a drag I still wouldn't suggest using that big of a block. The 598 wouild guzzle probably about 2x more gas than you are using now. If you are looking for a huge gain in power... think about a centrifigal supercharger throw in 10 psi and you can add another 200 or 300 horses without even being intercooled and still run pump gas. You would spend less money and end up with probably more horses than if you bought the block and all the parts for the 598.