[Travis Q]

Here's what I would do, for whatever that's worth.

Give the block a good deburr. No need for anything terribly fancy, just clean up any flash and sharp stuff that could be a starting point for cracks, especially around the main webs.

I would give the block an extra little bit of piston to wall clearance. Call the piston mfg, and tell them what you're doing with it. A lot depends on what alloy the pistons are made of.

The piston ring end gaps need to be a little bit looser than a naturally aspirated engine. How much looser depends on your ring choice. What's the bore size? What piston ring pack is the piston set up for?

At this power level, bearing clearances should be close to whatever you would run with a NA engine.

I wouldn't worry too much about a block fill.

Good fasteners are always a good investment. I prefer head studs, regardless of power level, but if you can't swing that, at least use a good head bolt and main bolt.

500 hp should be no problem at all. At 10-12 psi, I would not be surprised at all with 600 hp or more.