this has been been beat to death im sure but out of curiosity i was looking for casting numbers on my 99 block and i found a 2 on the one side and the letter A on the other side...did a ton of searching and have never seen any of them mentioned or any mention of the letter A. both were on the side above the pan towards the front of the block

 

If its not a 53 you have nothing to worry about

 

ya i know....i was just curious since there was a letter on the one side...havent heard of that before

 

Keep looking. If there's some stamped numbers, it might be a heavy/stout mexican block.

http://www.stamey.info/Truck/Cummins53BlockFAQ.htm

 

ive read all i could find on where the numbers are...crawled under both sides with the flashlight... only thing i could see was the 2 on the one side and the A on the other...both in about the location of where the 53 should be..if its there.

both the 2 and the A were stamped letters....maybe 1/2-3/4 in tall