more engine numbers

A V-8 has been installed in a small Blazer I just bought, and the SMOG inspector requires the exact year and model of the car it came out of.

So, I recently asked about location of engine numbers on this site , and I was told (and have now found it) that there is a serial number on the front of the block on the passenger side. However, this serial number doesn't give all the info about the engine.
Apparently, there is also a second number, a so called casting number, located on the back of the engine, driver's side. I tried for about 15 minutes to find this number with a mirror and a flashlight, but no luck.
Am I correct in assuming that you cant read this number without removing the whole darn engine ? Is there a trick to this ?
Thanks Felix
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