Max Bore on a 98 Magnum 360?

Well, we're talking two seperate things then. He is measuring the existing bore, and using experience and the factory published max overbore (ID) dimension for his figuring. That doesn't take anything into account except published specs. In a typical rebuild, that is more than enough. But, you are asking the block to exceed the factory design in terms of power and stress. So where the typical rebuild "should" be fine at .020 or .030 over, a performance engine may not have as good a service life when built on that platform. You have to dig a little deeper. What would be the best is letting the builder see how thick the casting for each bore is. That is what the term sonic testing is. It allows the builder to "see" the thickness of a metal. So you know if you're going too far with an overbore for a given application. Think of it this way. If you're tunring into a garage, and the insdie wall in 5' thick, and the outside wall is a std 1' thick, you may not fit in that spot. Or, you may fit the car, but not be able to get out of the vehicle...lol Same thing with sonic testing. It tells you what you cant see, so you can make a decision based on fact, not published semi fiction.