I've never seen or heard of any 4AGE busting a block. There may be more flex leading to more chance of other problems, however I think you'd have to be getting pretty extreme before that became a problem.
Many years ago I saw a Road and Track (they know about 4As from plenty of hands on experience) display engine at an event. It was a serious build (200+hp??) and used the 3rib block. While I was there someone mentioned the 3 ribs, and Terry replied that it was no issue.
Hen