Here's how it appears on a truck SPID from the era.

In this case the engine is an L47, with an ECL of "20" (whatever that means, as you say).

The ECL describes additional detail beyond the RPO, defining proliferation for that component. For an engine, it might define AC vs None, multiple carb vs single, manual trans vs auto, California vs Federal emissions, etc. For a rear axle, it would define ratio, locking vs open, perhaps special brake friction material, etc.

So while we know what the ECL does - we don't necessarily have the secret decoder ring.

K

By the time I started with GM (1979) the ECL fell into disuse, so I don't have any firsthand experience with it.

Broadcast codes were still used on the build sheet to facilitate the operations on the line but were no longer reported on the SPID label.

K

Go to the link in post #3 above, which shows some of it and discusses other known documentation of that car. It was a COPO car, with a specific COPO number for that one engine, which COPO number appears on the window sticker.

Correct. But one was crushed (as both were supposed to have been) and was not sold to the public. So it was not added to the tally of coupes built.

Keith, I've been meaning to follow up with this but life got in the way--stay tuned.

Gonna be in Stanton this weekend?

Thanks for the note; no - I've got some other commitments this weekend that will keep me away.

Have fun!

K

Here is a white Z16 left over ,no big block , has convertible frame with Z16 marking, 160-mph speedometer ,hand cut firewall,etc. Has binders of factory paperwork. This is how it came from the factory but with a SB and painted white.
Another Bellaire Ohio car. Lean to roof fell on it during a storm. A collector has it now and is restoring it.

What makes it a Z16 if it was built by the factory with a small block?

I never said it was a z16. It came from the factory with all the z16 parts except the BB