I remember a post thought I saved the info but can't find it now someone posted casting numbers or some identifing numbers for thin wall mega blocks I know some were thin in the early years I tried the search funtion with no luck

PM Bob George on this board, he knows the casting numbers, along with most any other thing you might have questions on

The one im using has a sticker on the rear of the block that says,DO NOT EXCEED 4.500 BORE .I guess thats the reason,must be thinner than normal. Its a 572cu,572 heads and 350 nos and doesn't seem to have a problem with this . ????

Later thin wall blocks were stickered do not exceed 4.310 or other demensions.If the sticker is gone you must sonic test.Be cautious and check all bores at all locations,some blocks may have only a few thin cylinders resulting from core shift.All early blocks cast in the early 1990s with stamped serial numbers 360 or lower were junk.