[unruhjonny]

Here's how I have understood it;

• The air cleaner lid was a part of the engine package.
• For 1970 & earlier, chrome valve covers and air cleaner lids were included (as an engine dress up) on the Grand Prix, GTO & Firebird 400/4bbl engines.
• After 1970 NO engine came with the chrome dress up (valve covers and air cleaner lid); so after 1970 the only way to get it was over the counter at the parts department.

Does that clear matters up?

Just ot muddy the waters a bit;
For 1970 & prior, a special air cleaner assemblies circumvented the chrome lid being included with the engine dress up.
EG: 1970 Trans Am used a shaker assembly, an the included lid was NOT chrome.