On engines from that era I have seen data plates that were stamped out and attached to the engine, not stamped into the engine as was common with US cars.

Over time these plates fall off or get knocked off when the engine is rebuilt.

Look for the plate on the side of the block. They are usually towards the rear on the side. You may find only some holes where the rivets once were. The engine plates are about two inches or so long and about .5 inches high. They are black with white letters.

And they are usually on the left side of the block since the manifolds were on the right. They can still be covered up by plumbing or grease or just caked on dirt.