360 engine core question

If the block passes a crack check and has a standard bore, i would do a sonic check to see how far you can overbore it safely.
They are usually fine at .030 over, any more and i would seriously consider a sonic check to be safe.
I take it you just want the block and caps, so the crank, rods, and pistons don't matter to you.
For the block only, i would say that $200 would be a good deal.