I can't see the sides of block to well because of shields, are there extra ribs, more than a stock 440? Early industrial blocks had these and much thicker clyinder walls. I had a 426 block out of a 40 ton crane, when bored 60 over the machinist said it was the only block that ever "sang" to him. Replaced my TMC 426 HP block. Maybe these newer ones are the thin wall blocks you hear about. Still an excellent purchase.