Slant 6 block casting numbers

There is a table of casting #'s at slantsix.org. I have it at home. You can find here if you search (from ggogle works best for me). Early blocks had 3 staggered "core plugs". By the 1970's there were 5 in a row. The last engines (late 70's) had "peanut heads", without the removable aluminum spark plug tubes, but may have been swapped onto an earlier block.