I think the crank stiffness can be increased by using a forged crank, which distributes the load more evenly to the mains. Billet main caps also help (usually the two center caps). All this protects the block.
The block girdle (RJC) helps to stiffen the block.
Might want to find out if the deck height is the same as the 109 block. Some of these blocks had taller decks.