Well I was making 630hp before this happened, and would not mind going up some. may not require a dart block, but it would be nice. Ateco advertises a 540 or 555 short block for $4400 plus shipping, not a whole lot more then the $3500 I was looking at.
My rods from my 509 are still good as well as the pistons and heads, had scat h-beams and srp pistons, may look for gen v block, but all I can find here are 454 blocks for cheap.

Look around, check racingjunk, ask the machine shops in oyur area. A buddy of mine just sold a 502 Gen VI block for cheap.

I was just trying to help.... it's totally up to you. If it were me, I'd find a good block and re-use all my stuff.