Thanks guys.

So know one know what a small "2" mean in the casting number?

I don't think it means anything. All I could speculate is they assigned that pn ahead of time in GM documentation, and the size of the 2 could have given engineering a way to run 2 different block designs with the same frozen pn they could not change. That's all I can think of. Small 2 could be first run, and if they had problems, then the large 2 is the second run before the block was released for use in the camaro and the 2 vettes. Who knows. Odd things happen to low production special things.