Truthfully, IMO for what you are wanting to do I'd find a used, running, seasoned block that has 30-100k miles on it! It's always been racer/machine shop rule to find a block that's run fine with no issue for many miles and build upon this. Reasoning why is called " Core Shift" and its basically wear in the molds and adjoining parts that results in heads,intakes, blocks, and any cast piece you can think of not being 100% identical to its thousands of siblings!
Again, this is my opinion and what's been good for me.
Flip side is many racers with money start with a fresh (CNC block) that ensures correct measurements and identical twins time after time. :rock: