What is the difference between the 5.3 and the 6.0 blocks that allow the 6.0 to be bored 4.0+ and the 5.3 only to be bored to 3.910?

Are the water jackets in the 6.0 block smaller allowing for thicker cylinder walls? The 5.3 and the 6.0 have the same dimensions except for cylinder bores, right?

And both blocks can except a maximum of 4.125 crank, right? Can this be done without block clearancing?

=Dave