In all fairness to Unc-T the evolution of FE blocks (reinforcements/factors/features that strengthen the blocks is vague at best. From my own experience I still find the 427s essentially square cylinder wall thickness impressive for strength/stability of the cylinder walls. The 427s wall thicknes is typically sonic measured at 12:00, 3:00, 6;00...... Conversely IF bores are sonic'd at 1:30, , 4:30 , 7:30 and 10:30 wall thicknesses can be huge, so thick that if they were at 12:00, 3:00, 6;00 etc the walls would be: In the context of an internal combustion engine, "siamese bore" refers to a specific configuration where adjacent cylinder bores are directly connected by a solid metal bridge, rather than having a cooling passage between them. This means there's no coolant flow between the cylinders in that area.
Simply the support/thrust of the pistons is enhanced by these thick wall "I beams" 1:30, , 4:30 , 7:30 and 10:30 wall thicknesses
This is why a questionably thin sonic'd block should not be rejected. Is this thick wall indexing strengthening viable in other FEs or series motors ?..... I don't have a dam clue. But it dam well makes it clear FoMoCo didn't have to pay a penny more to casting.