All I can add is when they did the extensive sonic testing on BB's way back & found that there were alot of later(75-76) BB's that were actually tested better than the early ones that were supposed to be thicker I decided to sonic check my next build. I might not be in the danger zone with 30 over as mentioned but KNOWING FOR SURE is peace of mind.

I read the magazine article where they sonic tested a bunch of big blocks and found no real difference in cylinder wall thickness, but the earlier blocks had a higher nickle content in the iron. I don't have pictures of my '71 360 block, I just remember when I was tapping the main cap threds that the '71 block bottomed out and the '76 block, the tap would go all the way through. This caused me to look at the main webbing side-by-side, and there is a big difference in the thickness. I don't know if it really makes much difference unless your really pushing alot of power. The 360 is still sitting in my parents garage so it would be interesting to have it sonic checked. When I got the engine it was already 0.040" over.