No. That number would be the actual block casting numer or "part number". The block casting numbers for a HT502 and ZZ502 will be the same since the same block is used for both applications. But the serial number GM assigned to that engine will determine if it started life as a HT or ZZ. Similar to a VIN # on a car. That serial number and other info is stamped on a thin plate like a credit card and attached to the block near the fuel pump boss.
Brian Hobaugh SCCA National Tour June 2014
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