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I can't tell for sure from your pics, but here is a link to some info that might be helpful. http://www.stamey.info/truck/cummins53blockfaq.htm
http://image.trucktrend.com/f/35745...103dp_cummins_fatal_flaws+engine_on_stand.jpg
This picture helped me figure out exactly where to look on the driver side of my block.
That's how my truck is, no number, which I understand to mean I don't have a 53 block. I've seen one truck with a 53 block on a car lot and it was easy to see, like in the pictures.