Could use a little guidance on my build. Small block stuff
Option #1 and no nitrous until you tune the current combo
That's what I would do.
x2
I think a stock engine block will hold up just fine at 600hp on a turbo.
The reason being is that even though turbochargers have inherently high HP numbers, they are on a super lazy curve, because it comes in late. This is a good thing on hard parts and the power is there, when you can use it.
I would set up a magnum, to avoid the need for heavy metal oils.
I would also opt for 8:1 or 8.5:1 on a 408 stroked magnum or roller LA block to begin with, on some cometic gaskets with a 65 or better RMS cut on the deck and head for good seal.
The magnum heads are closed chamber, I'd go aftermarket there, maybe opt for some edelbrocks and go over them really good on a flow bench, port matched to a good single plane. The Magnum exhaust is good looking, but if you can't get the math right for 8.5:1, you could look for a roller LA and go with open heads. Preferably some early to mid seventies 360, for the better exhaust.
If you don't want to deal with a turbo hat and a carb that is good enough to hold up to 15-17psi, you can always build a box to go around the carb to pressurize the entire thing.