Safely? most blocks will take a 30 thou overbore, after that it can get close in places.
My XF was rebored and the block cleaned up. Crank reground, new pistons, whole assembley balanced, head ported and oversize valves installed, big cam, new lifters and valve springs, good set of extractors and a redline 4bbl intake with a 465 holley.
The HP is not this engine's big mover, its the big flat torque curve that climbs to 440nm at 2500rpm (when the converter locks up) and slowly moves up to 460nm at 3100rpm (peak) then slowly drops off to 440nm around 4200rpm.
The engine is still pumping out just over 400nm when peak HP is reached but it drops off quickly after that. This is looking at the RW dyno print out.
Just like a Tsunami.