[Kurt S]

One thing is for sure: an engine code was only stamped on the pad for a complete engine assembly (manifolds, dist, etc).

I think the LS6 OTC motors are the exception, not the rule.
Very few motors had a service part # for a totally complete assembly. The LS6 did, so they used the CRR engine code and ran it right down regular production line.

Other service motors were not complete assemblies and thus were not stamped with the application code, but as CE blocks.

Never seen a VIN stamped on a CE block. The dealers were also supposed to stamp the delivery date on the VIN tag up to 67. How many did??

I've never got a satisfactory answer on what happened to extra production motors. I'm digging again.
I do know they worked hard (and still do) to balance out the build so they used everything up to make room for the new model parts. Only so much room in the plant......